[clang] [Driver] Teach Barmetal toolchain about GCC installation(1/3) (PR #121829)

[Petr Hosek via cfe-commits]

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@@ -110,20 +111,93 @@ static std::string computeBaseSysRoot(const Driver &D, bool IncludeTriple) {
   return std::string(SysRootDir);
 }
 
+// GCC sysroot here means form sysroot from either --gcc-install-dir, or from
+// --gcc-toolchain or if the toolchain is installed alongside clang in
+// bin/../<TargetTriple> directory if it is not explicitly specified on the
+// command line through `--sysroot` option. libc here will be newlib.
+std::string BareMetal::computeGCCSysRoot() const {
+  if (!getDriver().SysRoot.empty())
+    return getDriver().SysRoot;
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petrhosek wrote:

This check shouldn't be necessary.

https://github.com/llvm/llvm-project/pull/121829