Have FreeBSD use even more of the same smarts as Linux is now using for
adding search paths. Add them only when they exist, and prefix the paths
with the sysroot. This will allow targeting a FreeBSD sysroot on
a non-FreeBSD host machine, and perhaps more importantly should allow
testing the FreeBSD driver's behavior similarly to the Linux tests with
a fake tree of files in the regression test suite.

I don't have FreeBSD systems handy to build up the list of files that
should be used here, but this is the basic functionality and I'm hoping
Roman or someone from the community can contribute the actual test
cases.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@148940 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Driver/ToolChains.cpp b/lib/Driver/ToolChains.cpp
index 6b8168e..e50ab754 100644
--- a/lib/Driver/ToolChains.cpp
+++ b/lib/Driver/ToolChains.cpp
@@ -1623,6 +1623,10 @@
   return *T;
 }
 
+static void addPathIfExists(Twine Path, ToolChain::path_list &Paths) {
+  if (llvm::sys::fs::exists(Path)) Paths.push_back(Path.str());
+}
+
 /// FreeBSD - FreeBSD tool chain which can call as(1) and ld(1) directly.
 
 FreeBSD::FreeBSD(const HostInfo &Host, const llvm::Triple& Triple)
@@ -1633,9 +1637,9 @@
   // for the remaining cases.
   if (Triple.getArch() == llvm::Triple::x86 ||
       Triple.getArch() == llvm::Triple::ppc)
-    getFilePaths().push_back("/usr/lib32");
+    addPathIfExists(getDriver().SysRoot + "/usr/lib32", getFilePaths());
 
-  getFilePaths().push_back("/usr/lib");
+  addPathIfExists(getDriver().SysRoot + "/usr/lib", getFilePaths());
 }
 
 Tool &FreeBSD::SelectTool(const Compilation &C, const JobAction &JA,
@@ -1929,10 +1933,6 @@
   return UnknownDistro;
 }
 
-static void addPathIfExists(Twine Path, ToolChain::path_list &Paths) {
-  if (llvm::sys::fs::exists(Path)) Paths.push_back(Path.str());
-}
-
 /// \brief Get our best guess at the multiarch triple for a target.
 ///
 /// Debian-based systems are starting to use a multiarch setup where they use