[builtins][ARM] Replace call_apsr.S with inline asm

The %arm_call_apsr expansion doesn't work when config.clang is a clang
driver defaulting to a non-ARM arch. Rather than fix it, replace
call_apsr.S with inline asm in call_apsr.h, which also resolves the
FIXME added in D31259.

Maybe the `__attribute__((noinline,pcs("aapcs")))` attributes are
unnecessary on the static functions, but I was unsure what liberty the
compiler had to insert instructions that modified the condition codes,
so it seemed helpful.

Differential Revision: https://reviews.llvm.org/D82147