Shaders: have a dedicated resource list on ES2 builds.

There are no geometry shaders, and gradually more and more shaders will
be ES3+ only.

src/Magnum/Shaders/CMakeLists.txt

@@ -31,7 +31,11 @@ if(NOT MAGNUM_WITH_GL)
     message(SEND_ERROR "Shaders are available only if MAGNUM_WITH_GL is enabled")
 endif()
 
-corrade_add_resource(MagnumShaders_RESOURCES_GL resources-gl.conf)
+if(MAGNUM_TARGET_GLES2)
+    corrade_add_resource(MagnumShaders_RESOURCES_GL resources-gles2.conf)
+else()
+    corrade_add_resource(MagnumShaders_RESOURCES_GL resources-gl.conf)
+endif()
 
 set(MagnumShaders_SRCS
     ${MagnumShaders_RESOURCES_GL})

src/Magnum/Shaders/resources-gles2.conf

@@ -0,0 +1,46 @@
+group=MagnumShadersGL
+nullTerminated=true
+
+[file]
+filename=Flat.vert
+
+[file]
+filename=Flat.frag
+
+[file]
+filename=FullScreenTriangle.glsl
+
+[file]
+filename=generic.glsl
+
+[file]
+filename=MeshVisualizer.vert
+
+# MeshVisualizer.geom missing
+
+[file]
+filename=MeshVisualizer.frag
+
+[file]
+filename=Phong.vert
+
+[file]
+filename=Phong.frag
+
+[file]
+filename=Vector.vert
+
+[file]
+filename=Vector.frag
+
+[file]
+filename=DistanceFieldVector.frag
+
+[file]
+filename=VertexColor.vert
+
+[file]
+filename=VertexColor.frag
+
+[file]
+filename=compatibility.glsl