[flang] Add driver install directory to AIX toolchain program paths l…

…ist.

flang-new encounters an issue where its unable to invoke itself because the
install directory was missing from the program paths on AIX.

Reviewed By: w2yehia

Differential Revision: https://reviews.llvm.org/D140628

clang/lib/Driver/ToolChains/AIX.cpp

@@ -287,6 +287,10 @@ void aix::Linker::ConstructJob(Compilation &C, const JobAction &JA,
 /// AIX - AIX tool chain which can call as(1) and ld(1) directly.
 AIX::AIX(const Driver &D, const llvm::Triple &Triple, const ArgList &Args)
     : ToolChain(D, Triple, Args) {
+  getProgramPaths().push_back(getDriver().getInstalledDir());
+  if (getDriver().getInstalledDir() != getDriver().Dir)
+    getProgramPaths().push_back(getDriver().Dir);
+
   ParseInlineAsmUsingAsmParser = Args.hasFlag(
       options::OPT_fintegrated_as, options::OPT_fno_integrated_as, true);
   getLibraryPaths().push_back(getDriver().SysRoot + "/usr/lib");