Rollup merge of #133543 - mustartt:aix-lgammaf_r-shim, r=cuviper

[AIX] create shim for lgammaf_r

On AIX, we don't have 32bit floating point for re-entrant `lgammaf_r` but we do have the 64bit floating point re-entrant `lgamma_r` so we can use the 64bit version instead and truncate back to a 32bit float.

This solves the linker missing symbol for `.lgammaf_r` when testing and using these parts of the `std`.