[clang] [llvm] [MC] Make UseAssemblerInfoForParsing mostly true (PR #91082)

[via cfe-commits]

gulfemsavrun wrote:

We started seeing a build time regression in our Clang toolchain builders on Mac, and I bisected to this commit:

1) Build step took 1.7 hours in the last build before
https://luci-milo.appspot.com/ui/p/fuchsia/builders/prod/clang-mac-x64/b8747439072851399889/overview

2) Build step took 2.5 hours in the first build after
https://luci-milo.appspot.com/ui/p/fuchsia/builders/prod/clang-mac-x64/b8747425464531858929/overview

https://github.com/llvm/llvm-project/pull/91082