[Bug target/78945] [arm] libatomic inline asm is not compatible with armv7-m

[nsz at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78945

--- Comment #3 from nsz at gcc dot gnu.org ---
(In reply to Ramana Radhakrishnan from comment #2)
> A simple patch would be to check for __ARM_FEATURE_SAT in all those macros
> in exch_n.c along with HAVE_STREXB etc .. 

__ARM_FEATURE_SIMD32 seems to be the right feature test macro,
(_SAT is defined on armv7-m) and with that libatomic compiles.