linux.execve64 and linux.sigcontext test failures on recent (g)linux debug + release

xref #2868
xref #3256

The following tests FAILED:
8 - linux.execve32 (Failed)
9 - linux.execve64 (Failed)
68 - code_api|linux.sigcontext (Failed)

gcc (Debian 7.3.0-5) 7.3.0
Linux version 4.18.10-1rodete2-amd64 (glinux-team@google.com) (gcc version 7.3.0 (Debian 7.3.0-5)) #1 SMP Debian 4.18.10-1rodete2 (2018-10-09)

Tests above fail with debug + release.

8 - linux.execve32 (Failed)
Probably ok as libgcc 32-bit is missing on my machine.

9 - linux.execve64 (Failed)
Test output regular expression mismatching

ctest -V -I 9,9
UpdateCTestConfiguration from :/usr/local/google/home/hgreving/dynamorio/build/DartConfiguration.tcl
Parse Config file:/usr/local/google/home/hgreving/dynamorio/build/DartConfiguration.tcl
UpdateCTestConfiguration from :/usr/local/google/home/hgreving/dynamorio/build/DartConfiguration.tcl
Parse Config file:/usr/local/google/home/hgreving/dynamorio/build/DartConfiguration.tcl
Test project /usr/local/google/home/hgreving/dynamorio/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 9
Start 9: linux.execve64

9: Test command: /usr/local/google/home/hgreving/dynamorio/build/bin64/drrun "-stderr_mask" "0xC" "-dumpcore_mask" "0" "--" "/usr/local/google/home/hgreving/dynamorio/build/suite/tests/bin/linux.execve64" "/usr/local/google/home/hgreving/dynamorio/build/suite/tests/32bit/suite/tests/bin/linux.execve-sub32"
9: Test timeout computed to be: 1500
9: parent is running under DynamoRIO
9: parent waiting for child
9: child is running under DynamoRIO
9: ERROR in execve: No such file or directory
9: child has exited
1/1 Test #9: linux.execve64 ...................***Failed Required regular expression not found.Regex=[^parent is running under DynamoRIO
parent waiting for child
child is running under DynamoRIO
it_worked
running under DynamoRIO
child has exited
$
] 0.46 sec

68 - code_api|linux.sigcontext (Failed)
Test output regular expression mismatching

ctest -V -I 68,68
UpdateCTestConfiguration from :/usr/local/google/home/hgreving/dynamorio/build/DartConfiguration.tcl
Parse Config file:/usr/local/google/home/hgreving/dynamorio/build/DartConfiguration.tcl
UpdateCTestConfiguration from :/usr/local/google/home/hgreving/dynamorio/build/DartConfiguration.tcl
Parse Config file:/usr/local/google/home/hgreving/dynamorio/build/DartConfiguration.tcl
Test project /usr/local/google/home/hgreving/dynamorio/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 68
Start 68: code_api|linux.sigcontext

68: Test command: /usr/local/google/home/hgreving/dynamorio/build/bin64/drrun "-s" "90" "-quiet" "-debug" "-killpg" "-stderr_mask" "0xC" "-dumpcore_mask" "0" "-code_api" "--" "/usr/local/google/home/hgreving/dynamorio/build/suite/tests/bin/linux.sigcontext"
68: Test timeout computed to be: 1500
68: Sending SIGUSR1
68: xmm[0] = 0xdeadbeef 0xdeadbeef 0xdeadbeef 0xdeadbeef
68: xmm[1] = 0xbd5b7dde 0xbd5b7dde 0xbd5b7dde 0xbd5b7dde
68: xmm[2] = 0x7ab6fbbc 0x7ab6fbbc 0x7ab6fbbc 0x7ab6fbbc
68: xmm[3] = 0xf56df778 0xf56df778 0xf56df778 0xf56df778
68: xmm[4] = 0xeadbeef0 0xeadbeef0 0xeadbeef0 0xeadbeef0
68: xmm[5] = 0xd5b7dde0 0xd5b7dde0 0xd5b7dde0 0xd5b7dde0
68: xmm[6] = 0xab6fbbc0 0xab6fbbc0 0xab6fbbc0 0xab6fbbc0
68: xmm[7] = 0x56df7780 0x56df7780 0x56df7780 0x56df7780
68: xmm[8] = 0xffffffff 0xffffffff 0xffffffff 0xffffffff
68: linux.sigcontext: /usr/local/google/home/hgreving/dynamorio/src/suite/tests/linux/sigcontext.c:81: signal_handler: Assertion `fp->xmm_space[i * 4 + j] == 0xdeadbeef << i' failed.
1/1 Test #68: code_api|linux.sigcontext ........***Failed Required regular expression not found.Regex=[^Sending SIGUSR1
xmm\[0\] = 0xdeadbeef 0xdeadbeef 0xdeadbeef 0xdeadbeef
xmm\[1\] = 0xbd5b7dde 0xbd5b7dde 0xbd5b7dde 0xbd5b7dde
xmm\[2\] = 0x7ab6fbbc 0x7ab6fbbc 0x7ab6fbbc 0x7ab6fbbc
xmm\[3\] = 0xf56df778 0xf56df778 0xf56df778 0xf56df778
xmm\[4\] = 0xeadbeef0 0xeadbeef0 0xeadbeef0 0xeadbeef0
xmm\[5\] = 0xd5b7dde0 0xd5b7dde0 0xd5b7dde0 0xd5b7dde0
xmm\[6\] = 0xab6fbbc0 0xab6fbbc0 0xab6fbbc0 0xab6fbbc0
xmm\[7\] = 0x56df7780 0x56df7780 0x56df7780 0x56df7780
xmm\[8\] = 0xadbeef00 0xadbeef00 0xadbeef00 0xadbeef00
xmm\[9\] = 0x5b7dde00 0x5b7dde00 0x5b7dde00 0x5b7dde00
xmm\[10\] = 0xb6fbbc00 0xb6fbbc00 0xb6fbbc00 0xb6fbbc00
xmm\[11\] = 0x6df77800 0x6df77800 0x6df77800 0x6df77800
xmm\[12\] = 0xdbeef000 0xdbeef000 0xdbeef000 0xdbeef000
xmm\[13\] = 0xb7dde000 0xb7dde000 0xb7dde000 0xb7dde000
xmm\[14\] = 0x6fbbc000 0x6fbbc000 0x6fbbc000 0x6fbbc000
xmm\[15\] = 0xdf778000 0xdf778000 0xdf778000 0xdf778000
All done