[clang] [Clang] add option --offload-jobs=N (PR #135229)

[Artem Belevich via cfe-commits]

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@@ -1233,6 +1233,10 @@ def offload_compression_level_EQ : Joined<["--"], "offload-compression-level=">,
   Flags<[HelpHidden]>,
   HelpText<"Compression level for offload device binaries (HIP only)">;
 
+def offload_jobs_EQ : Joined<["--"], "offload-jobs=">,
+  HelpText<"Set the number of threads for the clang-linker-wrapper. Defaults to"
+           " half of the available hardware threads if not specified.">;
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Artem-B wrote:

I'm fine with parallel jobs as an optional feature -- it is indeed useful in some situations. Interactive users, arguably, are a relatively small subset of users. Interactive use is mostly important for developers, so it's more visible to us, but there are way more builds done by the users and package maintainers who do not care about interactive performance, but do care about predictability and logistics of the builds, and will see little to no benefit in most cases, but for whom parallel sub-jobs will create headaches, if they are the default.

https://github.com/llvm/llvm-project/pull/135229