fix shellcheck error in 1990/stig/stig.sh

1990/stig/stig.sh

@@ -1 +1,2 @@
+#!/usr/bin/env bash
 alias c="cc -Wno-implicit-int -E -Dc='int main(){printf(\"N%sested comments allowed.\\n"'",/*/*/0*/**/1?"":"o n"'");}' stig.c|grep -v '^#'>o.c;cc -include stdio.h -o o o.c;./o"