Compilation error on linux mint 21.1

[Tmesys]

Describe the bug
Trying to buid Dr Memory from scratch on linux mint vera (gcc version 11.0.3).

To Reproduce

1. mkdir build.
2. cd build.
3. cmake ...
4. make

Screenshots or Pasted Text

```
[ 18%] Building C object drsyscall/CMakeFiles/drsyscall_static.dir/drsyscall_linux.c.o
/drmemory/drsyscall/drsyscall_linux.c: In function ‘handle_semctl’:
/drmemory/drsyscall/drsyscall_linux.c:981:9: error: ‘arg_val’ is used uninitialized [-Werror=uninitialized]
  981 |     arg = *(union semun *) &arg_val;
      |     ~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~
/drmemory/drsyscall/drsyscall_linux.c:975:15: note: ‘arg_val’ declared here
  975 |     ptr_int_t arg_val;
      |               ^~~~~~~
cc1: all warnings being treated as errors
make[2]: *** [drsyscall/CMakeFiles/drsyscall_static.dir/build.make:104 : drsyscall/CMakeFiles/drsyscall_static.dir/drsyscall_linux.c.o] Erreur 1
make[1]: *** [CMakeFiles/Makefile2:4620 : drsyscall/CMakeFiles/drsyscall_static.dir/all] Erreur 2
make: *** [Makefile:166 : all] Erreur 2

```

Versions

• Current git version (pulled today)
• Linux mint vera 21.1 X86_64

[derekbruening]

Whatever compiler version is on the regression tests is what is maintained: https://github.com/DynamoRIO/drmemory/blob/master/.github/workflows/ci-x86.yml#L43
For anything else you can submit a PR for a one-off fix, or even better help to upgrade those regression tests to Ubuntu 22.