games-action/xpilot: pass -std=gnu89

Does not build with `clang -std=c2x`, early workaround for
when this will become a default.

(not actively hunting for these, merely revisiting packages
previously looked at for clang16 even if not an issue "yet").

Signed-off-by: Ionen Wolkens <ionen@gentoo.org>

games-action/xpilot/xpilot-4.5.5-r1.ebuild

@@ -3,7 +3,7 @@
 
 EAPI=8
 
-inherit desktop toolchain-funcs
+inherit desktop flag-o-matic toolchain-funcs
 
 DESCRIPTION="Multi-player 2D client/server space game"
 HOMEPAGE="http://www.xpilot.org/"
@@ -49,6 +49,8 @@ src_prepare() {
 }
 
 src_configure() {
+	append-cflags -std=gnu89 # old codebase, incompatible with c2x
+
 	CC="$(tc-getBUILD_CC)" LD="$(tc-getLD)" \
 		IMAKECPP="${IMAKECPP:-${CHOST}-gcc -E}" xmkmf -a || die
 }