Use utils_getpid() and utils_gettid() in util_log_internal()

[ldorau]

Description

Use syscall(SYS_gettid) instead of gettid(),
because gettid() can be undefined in older OSes.

gettid() is undefined in CI OSes of OpenMP.

Checklist

• Code compiles without errors locally
• All tests pass locally
• CI workflows execute properly

[lplewa]

dito: you could remove gnusource define from file, and remove

[bratpiorka]

@vinser52 please rebase

[vinser52]

@vinser52 please rebase

@ldorau, I think it is a request to you.

[ldorau]

dito: you could remove gnusource define from file, and remove

@lplewa strerror_r() also requires _GNU_SOURCE to be defined:

/home/ldorau/work/unified-memory-framework/src/utils/utils_log.c: In function ‘util_log_internal’:
/home/ldorau/work/unified-memory-framework/src/utils/utils_log.c:128:25: error: initialization of ‘char *’ from ‘int’ makes pointer from integer without a cast [-Werror=int-conversion]
  128 |             char *err = strerror_r(saveno, err_buff, sizeof(err_buff));
      |                         ^~~~~~~~~~
cc1: all warnings being treated as errors

[ldorau]

@vinser52 please rebase

@ldorau, I think it is a request to you.

@vinser52 I think so ;-)
@bratpiorka Done.

[ldorau]

@bratpiorka @vinser52 Re-review please.