Tests: Add mixed Swift+CXX source test case

This test ensures we can configure and build mixed source binaries. The
test configures, but fails to verify due to multiple targets emitting
the `lib.c.o` and `lib.cpp.o` outputs. Both the clang build step and the
swift link step report that they emit the `lib.c.o` and `lib.cpp.o`
outputs. The `.o`'s are emitted by clang, not by swift.

1 files changed, 4 insertions, 0 deletions

diff --git a/Tests/SwiftMixLib/lib.c b/Tests/SwiftMixLib/lib.c
new file mode 100644
index 0000000..8eca512
--- /dev/null
+++ b/Tests/SwiftMixLib/lib.c
@@ -0,0 +1,4 @@
+int add_int(int a, int b)
+{
+  return a + b;
+}