Fix generators to make sure changes to rule inputs trigger correct rebuilds....

test/rules-rebuild/src/main.c

Index: test/rules-rebuild/src/main.c
===================================================================
--- test/rules-rebuild/src/main.c	(revision 0)
+++ test/rules-rebuild/src/main.c	(revision 0)
@@ -0,0 +1,12 @@
+#include <stdio.h>
+
+extern void prog1(void);
+extern void prog2(void);
+
+int main(int argc, char *argv[])
+{
+  printf("Hello from main.c\n");
+  prog1();
+  prog2();
+  return 0;
+}