[Solaris] Make RHEL devtoolsets handling Linux-specific

[ro]

Summary

This patch is meant to address the last outstanding review comment on the already approved
(but not yet commited) https://reviews.llvm.org/D35755, namely making the handling of the RHEL
devtoolsets Linux-specific.

Don't know if it's best integrated into the former or applied subsequently.

Tested on i386-pc-solaris2.11 and x86_64-pc-linux-gnu.

[fedor.sergeev]

LGTM

[ro]

Thanks for the quick review. Could you commit the base patch (which had been approved some time ago) and this one?

[fedor.sergeev]

I'm trying!
I had no access to Solaris box, and I finally got one yesterday, though it is rather old one and slow.
I plan to resolve it all till the end of this week.

[ro]

Excellent, thanks a lot.

cfe/trunk/lib/Driver/ToolChains/Gnu.cpp

for (vfs::directory_iterator LI = D.getVFS().dir_begin(PrefixDir, EC), LE;
         continue;
 
       Prefixes.push_back(CandidatePrefix);
     }
     return;
   }
 
   // Non-Solaris is much simpler - most systems just go with "/usr".
-  if (SysRoot.empty()) {
-    // Yet, still look for RHEL devtoolsets
-    // (should it be done Linux-only??)
+  if (SysRoot.empty() && TargetTriple.getOS() == llvm::Triple::Linux) {
+    // Yet, still look for RHEL devtoolsets.
     Prefixes.push_back("/opt/rh/devtoolset-6/root/usr");
     Prefixes.push_back("/opt/rh/devtoolset-4/root/usr");
     Prefixes.push_back("/opt/rh/devtoolset-3/root/usr");
     Prefixes.push_back("/opt/rh/devtoolset-2/root/usr");
-    Prefixes.push_back("/usr");
-  } else {
-    Prefixes.push_back(SysRoot.str() + "/usr");
   }
+  Prefixes.push_back(SysRoot.str() + "/usr");
 }
 
 /*static*/ void Generic_GCC::GCCInstallationDetector::CollectLibDirsAndTriples(
     const llvm::Triple &TargetTriple, const llvm::Triple &BiarchTriple,
     SmallVectorImpl<StringRef> &LibDirs,
     SmallVectorImpl<StringRef> &TripleAliases,
     SmallVectorImpl<StringRef> &BiarchLibDirs,
     SmallVectorImpl<StringRef> &BiarchTripleAliases) {