[ARM] Allow using ';' as asm statement separator in MSVC mode

This does the same as D96259, but for ARM, just like AArch64,
using the same comment char as for ELF and MinGW mode.

As the assembly input/output of LLVM is GAS style, trying to
match what MS armasm.exe does isn't needed (because the comment
char used is the least concern when it comes to that; all
directives differ too). If a separate armasm compatible mode
is implemented, it can use its own comment style (just like
llvm-ml implements MS ml.exe compatible assembly parsing).

This fixes building compiler-rt assembly files for ARM in MSVC
mode.

The updated testcase literals-comments.s was only intended to
make sure that '#' isn't interpreted as a comment char.

Differential Revision: https://reviews.llvm.org/D107251