Add rudimentary support for the Apple Swift language with Xcode

Allow the `Swift` language to be enabled with the Xcode generator for
Xcode >= 6.1.  Reject it on other generators and with older Xcode
versions.  Since Apple is the only vendor implementing the language
right now, the compiler id can be just `Apple`.

1 files changed, 4 insertions, 0 deletions

diff --git a/Tests/SwiftMix/CMain.c b/Tests/SwiftMix/CMain.c
new file mode 100644
index 0000000..13e2f8c
--- /dev/null
+++ b/Tests/SwiftMix/CMain.c
@@ -0,0 +1,4 @@
+extern int ObjCMain(int argc, char const* const argv[]);
+int main(int argc, char* argv[]) {
+  return ObjCMain(argc, argv);
+}