package/flutter-pi: enable vulkan if possible

Enable the flutter-pi vulkan option if a suitable driver is enabled.
Currently, only Mesa provides Vulkan drivers. As such, gating the
feature behind the BR2_PACKAGE_MESA3D_VULKAN_DRIVER option is
reasonable at the moment and is done by three other packages already:
flutter-engine, ivi-home screen, and wlroots.

Furthermore, a dependency on BR2_PACKAGE_VULKAN_LOADER is needed as the
vulkan-loader package provides the vulkan.pc file, which the configure step
relies upon.

Signed-off-by: Adam Duskett <adam.duskett@amarulasolutions.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

package/flutter-pi/flutter-pi.mk

@@ -24,7 +24,6 @@ FLUTTER_PI_CONF_OPTS = \
 	-DENABLE_TESTS=OFF \
 	-DENABLE_TSAN=OFF \
 	-DENABLE_UBSAN=OFF \
-	-DENABLE_VULKAN=OFF \
 	-DFILESYSTEM_LAYOUT=meta-flutter \
 	-DLINT_EGL_HEADERS=OFF \
 	-DTRY_BUILD_GSTREAMER_AUDIO_PLAYER_PLUGIN=OFF \
@@ -75,6 +74,13 @@ else
 FLUTTER_PI_CONF_OPTS += -DBUILD_TEXT_INPUT_PLUGIN=OFF
 endif
 
+ifeq ($(BR2_PACKAGE_MESA3D_VULKAN_DRIVER)$(BR2_PACKAGE_VULKAN_LOADER),yy)
+FLUTTER_PI_DEPENDENCIES += mesa3d vulkan-loader
+FLUTTER_PI_CONF_OPTS += -DENABLE_VULKAN=ON
+else
+FLUTTER_PI_CONF_OPTS += -DENABLE_VULKAN=OFF
+endif
+
 ifeq ($(BR2_PACKAGE_HAS_LIBGLES),y)
 FLUTTER_PI_CONF_OPTS += -DENABLE_OPENGL=ON
 else