Merge branch 'gles2-check-shader-once' into 'master'

Draft: render/gles2: check shaders once

See merge request wlroots/wlroots!4974

render/gles2/shaders/meson.build

@@ -14,6 +14,7 @@ foreach name : shaders
 		input: name,
 		output: name + '_check',
 		command: [glslang, '@INPUT@'],
+		capture: true,
 		build_by_default: true,
 	)