webkit-gtk: Set USE_PKGSRC_GCC_(RUNTIME) when building on NetBSD 9

We likely need this anyway since WebKit requires GCC 8 at minimum,
but forcing pkgsrc libgcc to be used (and thus bypassing the one
built with the custom build system in NetBSD that doesn't include
__fixdfti on aarch64) may be a useful workaround for PR toolchain/57022

www/webkit-gtk/Makefile

@@ -1,4 +1,4 @@
-# $NetBSD: Makefile,v 1.237 2022/09/16 19:56:33 leot Exp $
+# $NetBSD: Makefile,v 1.238 2022/09/25 08:57:51 nia Exp $
 
 DISTNAME=	webkitgtk-2.36.8
 PKGNAME=	${DISTNAME:S/webkitgtk/webkit-gtk/}
@@ -27,6 +27,13 @@ CTF_SUPPORTED=	no
 # GCC >= 8 is required, it no longer builds with lower versions.
 GCC_REQD+=		8
 
+.include "../../mk/bsd.prefs.mk"
+
+.if ${OPSYS} == "NetBSD" && ${OPSYS_VERSION} < 099915
+USE_PKGSRC_GCC=		yes
+USE_PKGSRC_GCC_RUNTIME=	yes
+.endif
+
 PKGCONFIG_OVERRIDE+=	Source/JavaScriptCore/javascriptcoregtk.pc.in
 PKGCONFIG_OVERRIDE+=	Source/WebKit/gtk/webkit2gtk-web-extension.pc.in
 PKGCONFIG_OVERRIDE+=	Source/WebKit/gtk/webkit2gtk.pc.in