[OpenMP] Fix a condition for KMP_OS_SOLARIS. (#71831)

Line 75 of `z_Linux_util.cpp` checks `#ifdef KMP_OS_SOLARIS` which is
always true regardless of the building platform because macro
`KMP_OS_SOLARIS` is always defined in line 23 of `kmp_platform.h`:
`define KMP_OS_SOLARIS 0`.

GitOrigin-RevId: 90a9e9f638073f46a36e0fda44948bc74da5f641
1 file changed