[clang] [Driver] Warn when using msan on Android (PR #122540)

[Thurston Dang via cfe-commits]

thurstond wrote:

> these checks into Toolchains/Linux.cpp so it triggers that code:

IMO adding the Android msan check into Toolchains/Linux.cpp would be cleaner because it's:
1) only a 1 or 2 line change (compared with the current ~10 lines)
2) this file handles all the broad compatibility checks. (SanitizerArgs.cpp uses err_drv_unsupported_opt_for_target only for niche checks.)

https://github.com/llvm/llvm-project/pull/122540