test: Add cases for C-mode gccxml-like output

Although gccxml did not support C, it was occasionally requested.  The
gccxml output format supports C and Clang can easily handle parsing it.
Add test cases that verify Clang can parse sources as C code and not
C++.

1 files changed, 1 insertions, 0 deletions

diff --git a/test/input/invalid.c b/test/input/invalid.c
new file mode 100644
index 0000000..2e739ef
--- /dev/null
+++ b/test/input/invalid.c
@@ -0,0 +1 @@
+class start;