[clang-cl] Allow a colon after /Fo option (#87209)
Modeled after
https://github.com/llvm/llvm-project/commit/8513a681f7d8d1188706762e712168aebc3119dd#
According to
https://learn.microsoft.com/en-us/cpp/build/reference/fo-object-file-name?view=msvc-170,
`/Fo` accepts a trailing-colon variant. This is also tested in practice.
This allows clang-cl to parse this.
I just copied one of the existing tests, let me know if this is not the
best way to do this. I tested that the test does not pass beofre the
Options.td change, and that it does after.
See also #46065
