[Flang] Compilation results in bogus movabsq instruction

I'm compiling the https://github.com/jacobwilliams/json-fortran/releases/tag/9.0.2 project with Flang 21.1.1

The compilation is successful, however running `make test` results in many tests crashing with SIGSEGV. Here's the backtrace for one of them:

```
Process 44846 stopped
* thread #1, name = 'jf_test_03', stop reason = signal SIGSEGV: invalid permissions for mapped object (fault address: 0x820d28cb0)
frame #0: 0x0000000820d28cb0
-> 0x820d28cb0: movabsq $0x8226946d0, %r11 ; imm = 0x8226946D0
0x820d28cba: movabsq $0x820d28c98, %r10 ; imm = 0x820D28C98
0x820d28cc4: jmpq *%r11
0x820d28cc7: addb %dh, 0x820d28e(%rax)
(lldb) bt
* thread #1, name = 'jf_test_03', stop reason = signal SIGSEGV: invalid permissions for mapped object (fault address: 0x820d28cb0)
* frame #0: 0x0000000820d28cb0
frame #1: 0x000000082269962d libjsonfortran.so.9.0`_QMjson_value_moduleFjson_traversePtraverse at json_value_module.F90:9590:9
frame #2: 0x000000082268c6f1 libjsonfortran.so.9.0`_QMjson_value_modulePjson_traverse at json_value_module.F90:9573:38
frame #3: 0x0000000822654831 libjsonfortran.so.9.0`_QMjson_value_modulePjson_check_all_for_duplicate_keys at json_value_module.F90:5823:9
frame #4: 0x00000008226740d7 libjsonfortran.so.9.0`_QMjson_value_modulePjson_parse_file at json_value_module.F90:9815:17
frame #5: 0x000000082269f276 libjsonfortran.so.9.0`_QMjson_file_modulePjson_file_load at json_file_module.F90:871:5
frame #6: 0x00000000002148e1 jf_test_03`_QMjf_test_3_modPtest_3 at jf_test_03.F90:57:5
frame #7: 0x0000000000215f11 jf_test_03`_QQmain at jf_test_03.F90:155:5
frame #8: 0x0000000000215f42 jf_test_03`main at jf_test_03.F90:158:1
frame #9: 0x0000000824dfec3a libc.so.7`__libc_start1 + 298
frame #10: 0x00000000002142d0 jf_test_03`_start at crt1_s.S:83
```

The problem persists even when compiling with `-O0 -g`.

Reproduce with Flang 21.1.1 by compiling json-fortran 9.0.2 and running `make test`, starting from the SIGSEGV in `json_value_module.F90` and the call path through `json_file_module.F90` and `jf_test_03.F90`. Compare the generated `movabsq` sequence under `-O0 -g`; done means the tests no longer crash and bogus instructions are absent.

Written by the indexing model from the issue text.