Driver: Add a --working-directory option which can be used to cause the compiler
to operate "as if" in a certain working directory.
 - For now, we just implement this by changing the actual working directory, but
   eventually we would want to handle this transparently. This is useful to
   avoid an extra exec() pair in some situations, and will be something we would
   want to support for more flexibility in using the Clang libraries.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@140409 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Driver/Driver.cpp b/lib/Driver/Driver.cpp
index ec9295d..d64eab5 100644
--- a/lib/Driver/Driver.cpp
+++ b/lib/Driver/Driver.cpp
@@ -323,6 +323,13 @@
   if (Args->hasArg(options::OPT_nostdlib))
     UseStdLib = false;
 
+  // Honor --working-directory. Eventually we want to handle this completely
+  // internally to support good use as a library, but for now we just change our
+  // working directory.
+  if (const Arg *A = Args->getLastArg(options::OPT__working_directory)) {
+    ::chdir(A->getValue(*Args));
+  }
+
   Host = GetHostInfo(DefaultHostTriple.c_str());
 
   // Perform the default argument translations.