Add support from compiling c from c3c.

resources/testproject/csource/test.c

@@ -0,0 +1,4 @@
+int test_doubler(int d)
+{
+	return d * d;
+}

resources/testproject/hello_world.c3

@@ -1,11 +1,13 @@
 module hello_world;
 import bar;
 
-extern fn void printf(char *hello);
+extern fn int test_doubler(int);
+extern fn void printf(char *, ...);
 
 fn int main(int x)
 {
     printf("Hello World!\n");
     bar::test();
+    printf("Hello double: %d\n", test_doubler(11));
     return 1;
 }

resources/testproject/project.toml

@@ -8,3 +8,7 @@ warnings = ["no-unused"]
 sources = ["./**"]
 # libraries to use
 libs = []
+# c compiler
+cc = "cc"
+# c sources
+csources = ["./csource/**"]