Merge 2de269a641e4ffbb7a44e559c4c0a91bb66df823 into 18.x

[brad0]

[OpenMP][AIX] Set worker stack size to 2 x
KMP_DEFAULT_STKSIZE if system stack size is too big (#81996)

This patch sets the stack size of worker threads to 2 x KMP_DEFAULT_STKSIZE (2 x 4MB) for AIX if the system stack size is too
big. Also defines maximum stack size for 32-bit AIX.

[brad0]

/cherry-pick 2de269a

[llvmbot]

@llvm/issue-subscribers-openmp

Author: Brad Smith (brad0)

[OpenMP][AIX] Set worker stack size to 2 x KMP_DEFAULT_STKSIZE if system stack size is too big (#81996)

This patch sets the stack size of worker threads to 2 x KMP_DEFAULT_STKSIZE (2 x 4MB) for AIX if the system stack size is too
big. Also defines maximum stack size for 32-bit AIX.

[llvmbot]

/pull-request #82146