media-video/mpv: disable broken cross-builds with raspberry-pi in 9999

Upstream now uses pkg-config to determine raspberry-pi compiler
flags instead of hardcoding them. Update the ebuild accordingly.

This is nice, but Gentoo tools are broken and don't work as advertised,
see Gentoo bug 607344. Thus, disable cross-builds with raspberry-pi for
now. The required bits are in ebuild, so power users can workaround it.

Package-Manager: Portage-2.3.3, Repoman-2.3.1
Closes: gentoo#3718

media-video/mpv/mpv-9999.ebuild

@@ -169,6 +169,12 @@ src_prepare() {
 src_configure() {
 	tc-export CC PKG_CONFIG AR
 
+	if tc-is-cross-compiler && use raspberry-pi; then
+		export EXTRA_PKG_CONFIG_LIBDIR="${SYSROOT%/}${EPREFIX}/opt/vc/lib/pkgconfig"
+		# Drop next line when Gentoo bug 607344 is fixed or if you fixed it locally.
+		die "${PN} can't be cross built with raspberry-pi USE enabled. See Gentoo bug 607344."
+	fi
+
 	local mywafargs=(
 		--confdir="${EPREFIX}/etc/${PN}"
 		--docdir="${EPREFIX}/usr/share/doc/${PF}"