freetype: enable-freetype-config build option for 2.9.1 (#9653)

This builds the 'freetype-config' binary which can be used to get
configuration information about the freetype install, used by some
dependents.

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

@@ -25,7 +25,10 @@ class Freetype(AutotoolsPackage):
     depends_on('pkgconfig', type='build')
 
     def configure_args(self):
-        return ['--with-harfbuzz=no']
+        args = ['--with-harfbuzz=no']
+        if self.spec.satisfies('@2.9.1:'):
+            args.append('--enable-freetype-config')
+        return args
 
     def setup_dependent_environment(self, spack_env, run_env, dependent_spec):
         spack_env.prepend_path('CPATH', self.prefix.include.freetype2)