[SFrame][Retry] Add assembler option --gsframe (#165806)
This plumbs the option --gsframe through the various levels needed to
support it in the assembler.
This is the final step in assembler-level sframe support for x86. With
it in place, clang produces sframe-sections that successfully link with
gnu-ld.
LLD support is pending some discussion.
The previous PR (https://github.com/llvm/llvm-project/pull/165322) had a
bad merge, but the only comments were as below. Both done.
1. Fix some stray formatting.
2. Add tests that:
the option is passed on to cc1
the correct error is emitted when an unsupported platform is used
the assembler behaves as expected (even if this has been tested
elsewhere, an end-to-end "integration" test would be useful)
The test for assembler behavior simply checks that an sframe section is
added, and is modeled after the similar one for crel.
