render/vulkan: add Vulkan renderer

This new renderer is implemented with the existing wlr_renderer API
(which is known to be sub-optimal for some operations). It's not
used by default, but users can opt-in by setting WLR_RENDERER=vulkan.

The renderer depends on VK_EXT_image_drm_format_modifier and
VK_EXT_physical_device_drm.

Co-authored-by: Simon Ser <contact@emersion.fr>
Co-authored-by: Jan Beich <jbeich@FreeBSD.org>

render/vulkan/meson.build

@@ -0,0 +1,38 @@
+msg = []
+if 'vulkan' in renderers
+	msg += 'Install "@0@" or pass "-Dvulkan=disabled" to disable it.'
+else
+	msg += 'Required for vulkan renderer support.'
+endif
+
+dep_vulkan = dependency('vulkan',
+	version: '>=1.2.182',
+	required: 'vulkan' in renderers,
+	not_found_message: '\n'.join(msg).format('vulkan')
+)
+
+if not dep_vulkan.found()
+	subdir_done()
+endif
+
+glslang = find_program('glslangValidator', native: true, required: false)
+if not glslang.found()
+	if 'vulkan' in renderers
+		error('\n'.join(msg).format('glslang'))
+	else
+		subdir_done()
+	endif
+endif
+
+wlr_files += files(
+	'renderer.c',
+	'texture.c',
+	'vulkan.c',
+	'util.c',
+	'pixel_format.c',
+)
+
+wlr_deps += dep_vulkan
+features += { 'vulkan-renderer': true }
+
+subdir('shaders')