buildsys: allow building with gcc-14

GCC-14 requires all functions to have an explicit return type.
An implicit return type is no longer supported. main() in the ncurses
link check was declared without return type. Add it to make this work
on GCC-14.

See also: https://gcc.gnu.org/gcc-14/porting_to.html

Signed-off-by: Marcus Haehnel <marcus.haehnel@kernkonzept.com>

extra/config/lxdialog/check-lxdialog.sh

@@ -43,7 +43,7 @@ trap "rm -f $tmp" 0 1 2 3 15
 check() {
         $cc -x c - -o $tmp 2>/dev/null <<'EOF'
 #include CURSES_LOC
-main() {}
+int main() {}
 EOF
 	if [ $? != 0 ]; then
 	    echo " *** Unable to find the ncurses libraries or the"       1>&2