add check for +x flag

.github/checks/Makefile

@@ -1,7 +1,7 @@
 
-.PHONY: check tabs lastline spaces
+.PHONY: checkstyle tabs lastline spaces noexec
 
-checkstyle: tabs lastline spaces
+checkstyle: tabs lastline spaces noexec
 
 tabs: tabs.sh
 	@./tabs.sh
@@ -11,3 +11,6 @@ lastline: lastline.sh
 
 spaces: spaces.sh
 	@./spaces.sh
+
+noexec: noexec.sh
+	@./noexec.sh

.github/checks/noexec.sh

@@ -0,0 +1,18 @@
+#! /bin/bash
+OLDCWD=`pwd`
+SCRIPT_PATH=`dirname $0`
+CHECK_PATH=.
+
+cd $SCRIPT_PATH/../../
+
+FILES=`find $CHECK_PATH -executable -type f \( -name \*.inc -o -name Makefile -o -name \*.cfg -o -name \*.\[chs\] -o -name \*.mac -o -name \*.asm -o -name \*.sgml \) -print`
+
+cd $OLDCWD
+
+if [ x"$FILES"x != xx ]; then
+    echo "error: executable flag is set for the following files:" >&2
+    for n in $FILES; do
+        echo $n >&2
+    done
+    exit -1
+fi