[driver] Before applying the working directory check if the input path
is absolute.

llvm-svn: 166808
diff --git a/clang/test/Driver/working-directory-and-abs.c b/clang/test/Driver/working-directory-and-abs.c
new file mode 100644
index 0000000..6738c77
--- /dev/null
+++ b/clang/test/Driver/working-directory-and-abs.c
@@ -0,0 +1 @@
+// RUN: %clang -working-directory=%S %S/working-directory-and-abs.c -fsyntax-only