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/shaders/meson.build

@@ -0,0 +1,20 @@
+vulkan_shaders_src = [
+	'common.vert',
+	'texture.frag',
+	'quad.frag',
+]
+
+vulkan_shaders = []
+foreach shader : vulkan_shaders_src
+	name = shader.underscorify() + '_data'
+	args = [glslang, '-V', '@INPUT@', '-o', '@OUTPUT@', '--vn', name]
+	header = custom_target(
+		shader + '_spv',
+		output: shader + '.h',
+		input: shader,
+		command: args)
+
+	vulkan_shaders += [header]
+endforeach
+
+wlr_files += vulkan_shaders