qt: fix macOS w/ AppleClang (mesa libs) (#16302)

Building the `py-jupyter` stack on macOS with AppleClang breaks on
the `py-qtconsole` -> `py-qtconsole` -> `qt +opengl` package build
environment setup with:
```
 ==> Error: AttributeError: Query of package 'mesa' for 'libs' failed
 ...
 ==> Error: Failed to install qt due to ChildError: AttributeError: Query of package 'mesa' for 'libs' failed
```

This tries to add more library targets build by `mesa` to avoid this.

var/spack/repos/builtin/packages/mesa/package.py

@@ -13,6 +13,7 @@ class Mesa(AutotoolsPackage):
      - a system for rendering interactive 3D graphics."""
 
     homepage = "http://www.mesa3d.org"
+    maintainers = ['v-dobrev']
 
     # Note that we always want to build from the git repo instead of a
     # tarball since the tarball has pre-generated files for certain versions
@@ -180,7 +181,8 @@ def configure_args(self):
     @property
     def libs(self):
         for dir in ['lib64', 'lib']:
-            libs = find_libraries('libGL', join_path(self.prefix, dir),
+            libs = find_libraries(['libGL', 'libOSMesa'],
+                                  join_path(self.prefix, dir),
                                   shared=True, recursive=False)
             if libs:
                 return libs