[lit] Rather than including stdio.h, forward-declare printf in TestConvenienceVariables.test

llvm-svn: 349573

lldb/lit/Driver/Inputs/hello.c

@@ -1,4 +1,4 @@
-#include <stdio.h>
+int printf(const char *format, ...);
 
 int main(int argc, char **argv) {
   printf("Hello World\n");