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

[pscoro]

Summary

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

[pscoro]

Ping.

This is a needed fix for AIX, the code is trivial and used similarly on other targets.

[pscoro]

I have added a couple more reviewers based on revision history of the file being modified. If anybody is aware of anybody else who should be aware of this revision that would be appreciated

[pscoro]

Ping

clang/lib/Driver/ToolChains/AIX.cpp

 //===--- AIX.cpp - AIX ToolChain Implementations ----------------*- C++ -*-===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
void aix::Linker::ConstructJob(Compilation &C, const JobAction &JA,
   const char *Exec = Args.MakeArgString(ToolChain.GetLinkerPath());
   C.addCommand(std::make_unique<Command>(JA, *this, ResponseFileSupport::None(),
                                          Exec, CmdArgs, Inputs, Output));
 }
 
 /// 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");
 }
 
 // Returns the effective header sysroot path to use.
 // This comes from either -isysroot or --sysroot.
 llvm::StringRef