package: gentoo: Add USE flags to build documentation and tests

Add two new use flags, doc and test, to select building of documentation
and tests instead of unconditionally disabling them.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Paul Elder <paul.elder@ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>

package/gentoo/media-libs/libcamera/libcamera-9999.ebuild

@@ -14,7 +14,7 @@ EGIT_BRANCH="master"
 LICENSE="LGPL-2.1+"
 SLOT="0"
 KEYWORDS="*"
-IUSE="udev"
+IUSE="doc test udev"
 
 RDEPEND="
 	>=net-libs/gnutls-3.3:=
@@ -29,8 +29,8 @@ DEPEND="
 
 src_configure() {
 	local emesonargs=(
-		-Ddocumentation=false
-		-Dtests=false
+		$(meson_feature doc documentation)
+		$(meson_use test)
 	)
 	meson_src_configure
 }