switch_processes test failures because of LD_LIBRARY_PATH

This seems to be a "revival" of #2028. All other tests pass.

The "switch_processes" tests pass when LD_LIBRARY_PATH contains not more than 4 entries:

$ LD_LIBRARY_PATH="a:b:c:d" ctest -R 'switch_processes' -VV
UpdateCTestConfiguration  from :/tmp/rr/build/DartConfiguration.tcl
UpdateCTestConfiguration  from :/tmp/rr/build/DartConfiguration.tcl
Test project /tmp/rr/build
Constructing a list of tests
Done constructing a list of tests
Updating test list for fixtures
Added 0 tests to meet fixture requirements
Checking test dependency graph...
Checking test dependency graph end
test 1434
    Start 1434: switch_processes

1434: Test command: /usr/bin/bash "source_dir/src/test/switch_processes.run" "switch_processes" "" "bin_dir" "120"
1434: Test timeout computed to be: 10000000
1434: Test 'switch_processes' PASSED
1/2 Test #1434: switch_processes .................   Passed    1.83 sec
test 1435
    Start 1435: switch_processes-no-syscallbuf

1435: Test command: /usr/bin/bash "source_dir/src/test/switch_processes.run" "switch_processes" "-n" "bin_dir" "120"
1435: Test timeout computed to be: 10000000
1435: Test 'switch_processes' PASSED
2/2 Test #1435: switch_processes-no-syscallbuf ...   Passed    1.77 sec

The following tests passed:
        switch_processes
        switch_processes-no-syscallbuf

100% tests passed, 0 tests failed out of 2

Total Test time (real) =   3.63 sec

and completely fails otherwise:

$ LD_LIBRARY_PATH="a:b:c:d:e" ctest -R 'switch_processes' -VV
UpdateCTestConfiguration  from :/tmp/rr/build/DartConfiguration.tcl
UpdateCTestConfiguration  from :/tmp/rr/build/DartConfiguration.tcl
Test project /tmp/rr/build
Constructing a list of tests
Done constructing a list of tests
Updating test list for fixtures
Added 0 tests to meet fixture requirements
Checking test dependency graph...
Checking test dependency graph end
test 1434
    Start 1434: switch_processes

1434: Test command: /usr/bin/bash "source_dir/src/test/switch_processes.run" "switch_processes" "" "bin_dir" "120"
1434: Test timeout computed to be: 10000000
1434: source_dir/src/test/util.sh: line 342: 3622140 Aborted                 (core dumped) _RR_TRACE_DIR="$workdir" test-monitor $TIMEOUT debug.err python3 $TESTDIR/$expectscript.py $RR_EXE $GLOBAL_OPTIONS replay -o-n -o-ix -o$TESTDIR/test_setup.gdb $replayargs
1434: Test 'switch_processes' FAILED: debug script failed
1434: --------------------------------------------------
1434: gdb_rr.log:
1434: 3622131: forking and exec'ing write_race-Oe0V77wjM...
1434: child 3622132
1434: GNU gdb (GDB) Red Hat Enterprise Linux 10.2-10.el9
1434: Copyright (C) 2021 Free Software Foundation, Inc.
1434: License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
1434: This is free software: you are free to change and redistribute it.
1434: There is NO WARRANTY, to the extent permitted by law.
1434: Type "show copying" and "show warranty" for details.
1434: This GDB was configured as "x86_64-redhat-linux-gnu".
1434: Type "show configuration" for configuration details.
1434: For bug reporting instructions, please see:
1434: <https://www.gnu.org/software/gdb/bugs/>.
1434: Find the GDB manual and other documentation resources online at:
1434:     <http://www.gnu.org/software/gdb/documentation/>.
1434:
1434: For help, type "help".
1434: Type "apropos word" to search for commands related to "word"...
1434: /tmp/rr/src/test/test_setup.gdb:7: Error in sourced command file:
1434: No symbol table is loaded.  Use the "file" command.
1434: Reading symbols from /tmp/rr-test-switch_processes-Oe0V77wjM/target_process-Oe0V77wjM-0/mmap_clone_41_write_race-Oe0V77wjM...
1434: Really redefine built-in command "restart"? (y or n) [answered Y; input not from terminal]
1434: Really redefine built-in command "jump"? (y or n) [answered Y; input not from terminal]
1434: Remote debugging using 127.0.0.1:17663
1434:
1434: --------------------------------------------------
1434:  ---> Reached target process 3622132 at event 1001.
1434: --------------------------------------------------
1434: Reading symbols from /lib64/ld-linux-x86-64.so.2...
1434: Reading symbols from /tmp/rr/build/lib/rr/librrpreload.so...
1434: Reading symbols from /usr/lib64/libdl.so.2...
1434: Reading symbols from /usr/lib/debug/usr/lib64/libdl.so.2-2.34-60.el9.x86_64.debug...
1434: BFD: warning: system-supplied DSO at 0x6fffd000 has a section extending past end of file
1434: 0x00007fd7cfb75efb in mprotect () at ../sysdeps/unix/syscall-template.S:117
1434: 117       T_PSEUDO (SYSCALL_SYMBOL, SYSCALL_NAME, SYSCALL_NARGS,
1434: (rr) r 1
1434: y
1434: r 1
0x00007fd7cfb75f01      117     T_PSEUDO (SYSCALL_SYMBOL, SYSCALL_NAME, SYSCALL_NARGS,
1434: The program being debugged has been started already.
1434: Start it from the beginning? (y or n) y
Starting program: /tmp/rr-test-switch_processes-Oe0V77wjM/target_process-Oe0V77wjM-0/mmap_clone_41_write_race-Oe0V77wjM 1
1434: 3622131: forking and exec'ing write_race-Oe0V77wjM...
1434: child 3622132
1434:
1434: --------------------------------------------------
1434:  ---> Reached target process 3622132 at event 532.
1434: --------------------------------------------------
1434: warning: Build ID mismatch between current exec-file /tmp/rr-test-switch_processes-Oe0V77wjM/target_process-Oe0V77wjM-0/mmap_clone_41_write_race-Oe0V77wjM
1434: and automatically determined exec-file /tmp/rr-test-switch_processes-Oe0V77wjM/target_process-Oe0V77wjM-0/mmap_clone_4_target_process-Oe0V77wjM
1434: exec-file-mismatch handling is currently "ask"
1434: Load new symbol table from "/tmp/rr-test-switch_processes-Oe0V77wjM/target_process-Oe0V77wjM-0/mmap_clone_4_target_process-Oe0V77wjM"? (y or n) --------------------------------------------------
1434: debug.err:
1434: timeout 120 exceeded
1434: ====== /proc/3622141/status
1434: [...]
1434: Detaching from program: /tmp/rr/build/bin/rr, process 3622143
1434: [Inferior 1 (process 3622143) detached]
1434: --------------------------------------------------
1434: Test switch_processes failed, leaving behind /tmp/rr-test-switch_processes-Oe0V77wjM and /tmp/rr/build/rr-test-switch_processes-O6fkgPKb4
1434: To replay the failed test, run
1434:   _RR_TRACE_DIR=/tmp/rr-test-switch_processes-Oe0V77wjM rr replay
1/2 Test #1434: switch_processes .................***Failed  Error regular expression found in output. Regex=[FAILED]124.97 sec
test 1435
    Start 1435: switch_processes-no-syscallbuf

1435: Test command: /usr/bin/bash "source_dir/src/test/switch_processes.run" "switch_processes" "-n" "bin_dir" "120"
1435: Test timeout computed to be: 10000000
1435: source_dir/src/test/util.sh: line 342: 3622614 Aborted                 (core dumped) _RR_TRACE_DIR="$workdir" test-monitor $TIMEOUT debug.err python3 $TESTDIR/$expectscript.py $RR_EXE $GLOBAL_OPTIONS replay -o-n -o-ix -o$TESTDIR/test_setup.gdb $replayargs
1435: Test 'switch_processes' FAILED: debug script failed
1435: --------------------------------------------------
1435: gdb_rr.log:
1435: 3622601: forking and exec'ing write_race-F3qJErQSZ...
1435: child 3622602
1435: GNU gdb (GDB) Red Hat Enterprise Linux 10.2-10.el9
1435: Copyright (C) 2021 Free Software Foundation, Inc.
1435: License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
1435: This is free software: you are free to change and redistribute it.
1435: There is NO WARRANTY, to the extent permitted by law.
1435: Type "show copying" and "show warranty" for details.
1435: This GDB was configured as "x86_64-redhat-linux-gnu".
1435: Type "show configuration" for configuration details.
1435: For bug reporting instructions, please see:
1435: <https://www.gnu.org/software/gdb/bugs/>.
1435: Find the GDB manual and other documentation resources online at:
1435:     <http://www.gnu.org/software/gdb/documentation/>.
1435:
1435: For help, type "help".
1435: Type "apropos word" to search for commands related to "word"...
1435: /tmp/rr/src/test/test_setup.gdb:7: Error in sourced command file:
1435: No symbol table is loaded.  Use the "file" command.
1435: Reading symbols from /tmp/rr-test-switch_processes-F3qJErQSZ/target_process-F3qJErQSZ-0/mmap_clone_39_write_race-F3qJErQSZ...
1435: Really redefine built-in command "restart"? (y or n) [answered Y; input not from terminal]
1435: Really redefine built-in command "jump"? (y or n) [answered Y; input not from terminal]
1435: Remote debugging using 127.0.0.1:18137
1435:
1435: --------------------------------------------------
1435:  ---> Reached target process 3622602 at event 1001.
1435: --------------------------------------------------
1435: Reading symbols from /tmp/rr/build/lib/rr/librrpreload.so...
1435: Reading symbols from /usr/lib64/libdl.so.2...
1435: Reading symbols from /usr/lib/debug/usr/lib64/libdl.so.2-2.34-60.el9.x86_64.debug...
1435: Reading symbols from /usr/lib64/libc.so.6...
1435: Reading symbols from /usr/lib/debug/usr/lib64/libc.so.6-2.34-60.el9.x86_64.debug...
1435: Reading symbols from /lib64/ld-linux-x86-64.so.2...
1435: BFD: warning: system-supplied DSO at 0x6fffd000 has a section extending past end of file
1435: 0x00007f06c5295efb in mprotect () at ../sysdeps/unix/syscall-template.S:117
1435: 117       T_PSEUDO (SYSCALL_SYMBOL, SYSCALL_NAME, SYSCALL_NARGS,
1435: (rr) r 1
1435: y
1435: r 1
0x00007f06c5295f01      117     T_PSEUDO (SYSCALL_SYMBOL, SYSCALL_NAME, SYSCALL_NARGS,
1435: The program being debugged has been started already.
1435: Start it from the beginning? (y or n) y
Starting program: /tmp/rr-test-switch_processes-F3qJErQSZ/target_process-F3qJErQSZ-0/mmap_clone_39_write_race-F3qJErQSZ 1
1435: 3622601: forking and exec'ing write_race-F3qJErQSZ...
1435: child 3622602
1435:
1435: --------------------------------------------------
1435:  ---> Reached target process 3622602 at event 518.
1435: --------------------------------------------------
1435: warning: Build ID mismatch between current exec-file /tmp/rr-test-switch_processes-F3qJErQSZ/target_process-F3qJErQSZ-0/mmap_clone_39_write_race-F3qJErQSZ
1435: and automatically determined exec-file /tmp/rr-test-switch_processes-F3qJErQSZ/target_process-F3qJErQSZ-0/mmap_clone_4_target_process-F3qJErQSZ
1435: exec-file-mismatch handling is currently "ask"
1435: Load new symbol table from "/tmp/rr-test-switch_processes-F3qJErQSZ/target_process-F3qJErQSZ-0/mmap_clone_4_target_process-F3qJErQSZ"? (y or n) --------------------------------------------------
1435: debug.err:
1435: timeout 120 exceeded
1435: ====== /proc/3622615/status
1435: [...]
1435: Detaching from program: /tmp/rr/build/bin/rr, process 3622617
1435: [Inferior 1 (process 3622617) detached]
1435: --------------------------------------------------
1435: Test switch_processes failed, leaving behind /tmp/rr-test-switch_processes-F3qJErQSZ and /tmp/rr/build/rr-test-switch_processes-Yha5Y4isb
1435: To replay the failed test, run
1435:   _RR_TRACE_DIR=/tmp/rr-test-switch_processes-F3qJErQSZ rr replay
2/2 Test #1435: switch_processes-no-syscallbuf ...***Failed  Error regular expression found in output. Regex=[FAILED]124.93 sec

0% tests passed, 2 tests failed out of 2

Total Test time (real) = 249.93 sec

The following tests FAILED:
        1434 - switch_processes (Failed)
        1435 - switch_processes-no-syscallbuf (Failed)
Errors while running CTest

Full log

Start with src/test/switch_processes.run and src/test/util.sh, then reproduce both ctest switch_processes cases with four and five LD_LIBRARY_PATH entries. Compare the failing replay logs and test_setup.gdb behavior; done means both switch_processes tests pass with the longer path.