meson: Don't build glsl compiler tests unless OpenGL is enabled

Since there are no other users of the glsl compiler.

Reviewed-by: Eric Engestrom <eric.engestrom@intel.com>

src/compiler/glsl/glcpp/meson.build

@@ -55,7 +55,7 @@ glcpp = executable(
   build_by_default : false,
 )
 
-if with_tests
+if with_any_opengl and with_tests
   modes = ['unix', 'windows', 'oldmac', 'bizarro']
   if dep_valgrind.found()
     modes += ['valgrind']

src/compiler/glsl/meson.build

@@ -258,6 +258,6 @@ glsl_test = executable(
   install : with_tools.contains('glsl'),
 )
 
-if with_tests
+if with_any_opengl and with_tests
   subdir('tests')
 endif