This reverts commit 2919222d80.
That commit broke backwards compatibility. Additionally, the
replacement, -Wa,-mimplicit-it, isn't yet supported by any stable
release of Clang.
See D102812 for a fix for the error cases when callers specify both
-mimplicit-it and -Wa,-mimplicit-it.
This is a GNU as and Clang cc1as option, not a GCC option.
Users should specify `-Wa,-mimplicit-it=` instead.
Note: mixing the -m option and the -Wa, option doesn't work
`-Wa,-mimplicit-it=never -mimplicit-it=always` =>
`clang (LLVM option parsing): for the --arm-implicit-it option: may only occur zero or one times!`
Reviewed By: nickdesaulniers, raj.khem
Differential Revision: https://reviews.llvm.org/D102568
Martin Storsjö