CI: Don't copy .m4 files if they already exists [gen-appimage]

utils/desktop/klkt.desktop

 [Desktop Entry]
 Version=1.0
 Type=Application
-Name=Klkt
+Name=klkt
 Icon=lektor
 GenericName=Lektor notification client
 Comment=Notification client for lektord

utils/desktop/lektord.desktop

 [Desktop Entry]
 Version=1.0
 Type=Application
-Name=Lektord
+Name=lektord
 Icon=lektor
 GenericName=Lektor deamon
 Comment=The lektor deamon

utils/scripts/validate.bash

@@ -63,7 +63,7 @@ function check_mkdir ()
 
 function check_autoreconf ()
 {
-    cp /usr/share/aclocal/*.m4 $LKT_DIR/config/m4/ || die "Failed to copy .m4 files to $LKT_DIR/config/m4"
+    check_cp --no-clobber /usr/share/aclocal/*.m4 $LKT_DIR/config/m4/
     (cd $LKT_DIR && autoreconf --install --force) || die "Failed to autoreconf the '$LKT_DIR' folder"
 }