Make the stack non-executable

Otherwise, binutil's ld will emit the following warning on each scc(1) invocation:

	ld: warning: _sys_brk.6l: missing .note.GNU-stack section implies executable stack
	ld: NOTE: This behaviour is deprecated and will be removed in a future version of the linker

diff --git a/include/scc/bits/scc/sys-scc.h b/include/scc/bits/scc/sys-scc.h
index 9d6ae86b..85a37ecd 100644
--- a/include/scc/bits/scc/sys-scc.h
+++ b/include/scc/bits/scc/sys-scc.h
@@ -13,6 +13,7 @@ char *sysincludes[] = {
 /* configure below your system linker command line */
 char *ldcmd[] = {
 	"-static",
+	"-z","noexecstack",
 	"-z","nodefaultlib",
 	%NOPIE%
 	"-o","%o",