media-video/ffmpeg: only add -latomic when supported by compiler/linker

Closes: https://bugs.gentoo.org/820095
Signed-off-by: Sam James <sam@gentoo.org>

media-video/ffmpeg/ffmpeg-4.4-r1.ebuild

@@ -455,7 +455,7 @@ multilib_src_configure() {
 	if use arm || use ppc ; then
 		# bug #782811
 		# bug #790590
-		extra_libs+="-latomic "
+		extra_libs+="$(test-flags-CCLD -latomic) "
 	fi
 
 	set -- "${S}/configure" \

media-video/ffmpeg/ffmpeg-9999.ebuild

@@ -59,7 +59,7 @@ LICENSE="
 	samba? ( GPL-3 )
 "
 if [ "${PV#9999}" = "${PV}" ] ; then
-	KEYWORDS="~alpha ~amd64 ~arm ~arm64 ~hppa ~ia64 ~mips ~ppc ~ppc64 ~sparc ~x86 ~amd64-linux ~x86-linux"
+	KEYWORDS="~alpha ~amd64 ~arm ~arm64 ~hppa ~ia64 ~mips ~ppc ~ppc64 ~riscv ~sparc ~x86 ~amd64-linux ~x86-linux"
 fi
 
 # Options to use as use_enable in the foo[:bar] form.
@@ -450,6 +450,13 @@ multilib_src_configure() {
 		$(multilib_native_enable manpages)
 	)
 
+	local extra_libs
+	if use arm || use ppc ; then
+		# bug #782811
+		# bug #790590
+		extra_libs+="$(test-flags-CCLD -latomic) "
+	fi
+
 	set -- "${S}/configure" \
 		--prefix="${EPREFIX}/usr" \
 		--libdir="${EPREFIX}/usr/$(get_libdir)" \
@@ -464,6 +471,7 @@ multilib_src_configure() {
 		--ranlib="$(tc-getRANLIB)" \
 		--pkg-config="$(tc-getPKG_CONFIG)" \
 		--optflags="${CFLAGS}" \
+		--extra-libs="${extra_libs}" \
 		$(use_enable static-libs static) \
 		"${myconf[@]}" \
 		${EXTRA_FFMPEG_CONF}