[clang][AIX]Fix -flto-jobs for AIX. (#67853)

Currently using the `-flto-jobs=N` option passes `-bplugin_opt:jobs=N`
to the AIX linker which is not a valid option. This PR seeks to change
this behaviour to instead pass `-bplugin_opt:-threads=N` to control the
level of concurrency during LTO builds.

clang/lib/Driver/ToolChains/CommonArgs.cpp

@@ -631,6 +631,7 @@ void tools::addLTOOptions(const ToolChain &ToolChain, const ArgList &Args,
 
   const char *PluginOptPrefix = IsOSAIX ? "-bplugin_opt:" : "-plugin-opt=";
   const char *ExtraDash = IsOSAIX ? "-" : "";
+  const char *ParallelismOpt = IsOSAIX ? "-threads=" : "jobs=";
 
   // Note, this solution is far from perfect, better to encode it into IR
   // metadata, but this may not be worth it, since it looks like aranges is on
@@ -690,8 +691,8 @@ void tools::addLTOOptions(const ToolChain &ToolChain, const ArgList &Args,
 
   StringRef Parallelism = getLTOParallelism(Args, D);
   if (!Parallelism.empty())
-    CmdArgs.push_back(
-        Args.MakeArgString(Twine(PluginOptPrefix) + "jobs=" + Parallelism));
+    CmdArgs.push_back(Args.MakeArgString(Twine(PluginOptPrefix) +
+                                         ParallelismOpt + Parallelism));
 
   // If an explicit debugger tuning argument appeared, pass it along.
   if (Arg *A =

clang/test/Driver/lto-jobs.c

@@ -17,3 +17,8 @@
 // RUN: FileCheck -check-prefix=CHECK-LINK-THIN-JOBS2-ACTION < %t %s
 //
 // CHECK-LINK-THIN-JOBS2-ACTION: "-mllvm" "-threads={{[0-9]+}}"
+
+// RUN: %clang --target=powerpc-ibm-aix -### %s -flto=thin -flto-jobs=5 2> %t
+// RUN: FileCheck -check-prefix=CHECK-AIX-LINK-THIN-JOBS-ACTION < %t %s
+//
+// CHECK-AIX-LINK-THIN-JOBS-ACTION: "-bplugin_opt:-threads=5"