From f0ecb3850d7825cd967d22c09ed73d990605c70b Mon Sep 17 00:00:00 2001
From: Patrick Oppenlander <patrick.oppenlander@gmail.com>
Date: Mon, 11 Jan 2021 10:39:27 +1100
Subject: [PATCH 3/3] clang: support expanding target triple in sysroot path

This allows clang to switch sysroot (or, more usefully, default sysroot)
based on target triple.

For example, configuring with

-DDEFAULT_SYSROOT=../TARGET

will automatically select a target specific sysroot one level up from
the clang binary location.
---
 clang/lib/Driver/Driver.cpp | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/clang/lib/Driver/Driver.cpp b/clang/lib/Driver/Driver.cpp
index ece8222dcf24..8a3b068d86b9 100644
--- a/clang/lib/Driver/Driver.cpp
+++ b/clang/lib/Driver/Driver.cpp
@@ -1121,6 +1121,13 @@ Compilation *Driver::BuildCompilation(ArrayRef<const char *> ArgList) {
                     .Default(SaveTempsCwd);
   }
 
+  // expand TARGET in sysroot path
+  if (!SysRoot.empty()) {
+    size_t pos{0};
+    while ((pos = SysRoot.find("TARGET", pos)) != std::string::npos)
+      SysRoot.replace(pos, 6, TargetTriple);
+  }
+
   setLTOMode(Args);
 
   // Process -fembed-bitcode= flags.
-- 
2.30.0