POWER: Increase macro size limit for AIX

Fix bfloat16_bits union so that it always the sizeof unsigned short for AIX.

AzureCI: move OSX-Clang jobs to macOS-12 to resolve setup/build timeouts

This patch increases the macro size limit from 4096 to 16384 to
allow compiling larger assembly files in AIX.
Tested with GCC and IBM Open XL C.

POWER10: Fix compilation issues with Open XL C

Fix build on Fujitsu A64FX

This patch removes intermediate m4 conversions used in sbgemm
compilation as it is not needed for .c files.
Tested on AIX with gcc and IBM Open XL C.

As cgemm and zgemm kernels are not optimized for big endian falling
back to POWER8 versions.  Tested on AIX using gcc and Open XL C.

Require "classic ld" with XCODE 15.x on Mac

Fix division by zero in [z]rotg

Correct function prototypes in f2c-converted sources (lapack-netlib and ctest)

powerpc: Fix build errors with Open XL C

This patch fixes errors when using Open XL C compiler on AIX.
Tested with gcc/xlf and ibm-clang/xlf compiler combinations.

Improve function prototypes to fix strict-prototype warnings

Loongarch64 fixed dynamic arch

powerpc: Fix build errors with xlf

This patch fixes errors when using xlf as fortran compiler on Linux.
Tested with gcc/xlf and clang/xlf compiler combinations.