Revert use of thin archives in 0.60 branch.

Some custom_target()s may want to receive "fat" archives, so making use
of thin static_library() archives conditional only on it not being
installed, and without the possibility of an override by the user, is
undesirable. In #9453 I propose adding a thin: kwarg defaulting to true,
but that's a new feature that can only land in 0.61.

mesonbuild/backend/ninjabackend.py

@@ -2789,7 +2789,7 @@ https://gcc.gnu.org/bugzilla/show_bug.cgi?id=47485'''))
             if target.import_filename:
                 commands += linker.gen_import_library_args(self.get_import_filename(target))
         elif isinstance(target, build.StaticLibrary):
-            commands += linker.get_std_link_args(not target.should_install())
+            commands += linker.get_std_link_args(False)
         else:
             raise RuntimeError('Unknown build target type.')
         return commands