devel/llvm15: arm fixes, lite default change

Change the lite flavor to default to BE_FREEBSD rather than BE_NATIVE to
allow its use in cross-build CI pipelines.

Backport fix for LLVM bug 61396. [0] This fixes miscompilation of gcc
on 32-bit arm.

Remove an obsolete patch which breaks arm64. [1]

PR: 271992 [0], 271616 [1]
Reported by: jfc@mit.edu [0,1]