Modular Codegen: Separate flags for function and debug info support

This allows using and testing these two features separately. (noteably,
debug info is, so far as I know, always a win (basically). But function
modular codegen is currently a loss for highly optimized code - where
most of the linkonce_odr definitions are optimized away, so providing
weak_odr definitions is only overhead)

llvm-svn: 300104
diff --git a/clang/test/Modules/Inputs/codegen-flags/use.cpp b/clang/test/Modules/Inputs/codegen-flags/use.cpp
new file mode 100644
index 0000000..378ff31
--- /dev/null
+++ b/clang/test/Modules/Inputs/codegen-flags/use.cpp
@@ -0,0 +1,5 @@
+#include "foo.h"
+void use() {
+  f1();
+  foo f;
+}