meson: opengl: fix extra lib prefix

The meson target was named 'libvlc_opengles' but meson automatically
adds a 'lib' prefix, producing 'liblibvlc_opengles.a'. Rename the
target to 'vlc_opengles' so the output match the intended name.

modules/video_output/opengl/meson.build

@@ -47,7 +47,7 @@ vlc_modules += {
 
 libvlc_opengles = []
 if opengles2_dep.found()
-    libvlc_opengles = static_library('libvlc_opengles',
+    libvlc_opengles = static_library('vlc_opengles',
                                      dependencies: [gl_common_dep, m_lib],
                                      c_args: '-DUSE_OPENGL_ES2')
 endif