[clang] [Clang] Make `-Xarch_` handling generic for all toolchains (PR #125421)

[Joseph Huber via cfe-commits]

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@@ -1115,14 +1117,13 @@ def fno_convergent_functions : Flag<["-"], "fno-convergent-functions">,
 
 // Common offloading options
 let Group = offload_Group in {
-def offload_arch_EQ : Joined<["--"], "offload-arch=">, Flags<[NoXarchOption]>,
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jhuber6 wrote:

Overloaded term that means different things in different places. The `arch` in the LLVM triple refers to `amdgcn` in `amdgcn-amd-amdhsa` since that's the actual CPU microarchitecture. The `arch` in `-march` refers to the specific machine name for the processor that's being targeted. `-Xarch_gfx908` is valid because the `-Xarch_` option in non-offloading use also minds to `-march=` arguments AFAICT.

https://github.com/llvm/llvm-project/pull/125421