[modules] When building a module, if there are multiple matches for a header
file in the loaded module maps and one of them is from the current module,
that's the right match.

llvm-svn: 240350
diff --git a/clang/test/Modules/Inputs/explicit-build-prefer-self/a.h b/clang/test/Modules/Inputs/explicit-build-prefer-self/a.h
new file mode 100644
index 0000000..d457612
--- /dev/null
+++ b/clang/test/Modules/Inputs/explicit-build-prefer-self/a.h
@@ -0,0 +1,2 @@
+// a
+#include "x.h"