arc-mesa: arc-mesa-9999 compiles

arc-mesa-9999 is based on Mesa master.
Mesa master no longer supports arguments like "dri_driver=,i915".
The leading comma generates an error.

This CL fixes that. It is based on: https://crrev.com/c/2275258

BUG=None
TEST=cros_workon-$BOARD start arc-mesa
     remove all patches from arc-mesa-9999.ebuild
     emerge-$BOARD arc-mesa
     compiles Ok.

Change-Id: I5dda7f7e76bb5eda6d673935769a5207a48af223
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/overlays/chromiumos-overlay/+/2286395
Commit-Queue: Ricardo Quesada <ricardoq@chromium.org>
Commit-Queue: Lepton Wu <lepton@chromium.org>
Tested-by: Ricardo Quesada <ricardoq@chromium.org>
Reviewed-by: Ilja H. Friedel <ihf@chromium.org>
Reviewed-by: Lepton Wu <lepton@chromium.org>
Auto-Submit: Ricardo Quesada <ricardoq@chromium.org>
diff --git a/media-libs/arc-mesa/arc-mesa-9999.ebuild b/media-libs/arc-mesa/arc-mesa-9999.ebuild
index cde8ecf..7c946e6 100644
--- a/media-libs/arc-mesa/arc-mesa-9999.ebuild
+++ b/media-libs/arc-mesa/arc-mesa-9999.ebuild
@@ -73,8 +73,9 @@
 # Think about: ggi, fbcon, no-X configs
 
 driver_list() {
-	local drivers="$(sort -u <<< "${1// /$'\n'}")"
-	echo "${drivers//$'\n'/,}"
+	local uniq_driver=($(printf "%s\n" "$@" | sort -u))
+	local IFS=,
+	echo "${uniq_driver[*]}"
 }
 
 pkg_setup() {
@@ -320,9 +321,9 @@
 		$(meson_use gles2)
 		$(meson_use selinux)
 		$(meson_use shared-glapi)
-		-Ddri-drivers=$(driver_list "${DRI_DRIVERS[*]}")
-		-Dgallium-drivers=$(driver_list "${GALLIUM_DRIVERS[*]}")
-		-Dvulkan-drivers=$(driver_list "${VULKAN_DRIVERS[*]}")
+		-Ddri-drivers=$(driver_list "${DRI_DRIVERS[@]}")
+		-Dgallium-drivers=$(driver_list "${GALLIUM_DRIVERS[@]}")
+		-Dvulkan-drivers=$(driver_list "${VULKAN_DRIVERS[@]}")
 		--buildtype $(usex debug debug release)
 		$(use cheets && echo "--cross-file=${ARC_CROSS_FILE}")
 		$(use cheets && echo "-Dplatform-sdk-version=${ARC_PLATFORM_SDK_VERSION}")
@@ -510,14 +511,12 @@
 	case $# in
 		# for enabling unconditionally
 		1)
-			DRI_DRIVERS+=",$1"
+			DRI_DRIVERS+=("$1")
 			;;
 		*)
 			if use $1; then
 				shift
-				for i in $@; do
-					DRI_DRIVERS+=",${i}"
-				done
+				DRI_DRIVERS+=("$@")
 			fi
 			;;
 	esac
@@ -527,14 +526,12 @@
 	case $# in
 		# for enabling unconditionally
 		1)
-			GALLIUM_DRIVERS+=",$1"
+			GALLIUM_DRIVERS+=("$1")
 			;;
 		*)
 			if use $1; then
 				shift
-				for i in $@; do
-					GALLIUM_DRIVERS+=",${i}"
-				done
+				GALLIUM_DRIVERS+=("$@")
 			fi
 			;;
 	esac
@@ -544,14 +541,12 @@
 	case $# in
 		# for enabling unconditionally
 		1)
-			VULKAN_DRIVERS+=",$1"
+			VULKAN_DRIVERS+=("$1")
 			;;
 		*)
 			if use $1; then
 				shift
-				for i in $@; do
-					VULKAN_DRIVERS+=",${i}"
-				done
+				VULKAN_DRIVERS+=("$@")
 			fi
 			;;
 	esac