Bootstrap pkg-config and cmake on MacOS (#30497)

These need to be installed in order to build so we can install them via
Homebrew. Do this by simply restoring the Homebrew bootstrapping logic
we had in place previously.

Fixes #27171.

python/servo/platform/macos.py

@@ -55,7 +55,19 @@ class MacOS(Base):
         return True
 
     def _platform_bootstrap(self, _force: bool) -> bool:
-        return self._platform_bootstrap_gstreamer(False)
+        installed_something = False
+        try:
+            brewfile = os.path.join(util.SERVO_ROOT, "support", "macos", "Brewfile")
+            output = subprocess.check_output(
+                ['brew', 'bundle', 'install', "--file", brewfile]
+            ).decode("utf-8")
+            print(output)
+            installed_something = "Installing" in output
+        except subprocess.CalledProcessError as e:
+            print("Could not run homebrew. Is it installed?")
+            raise e
+        installed_something |= self._platform_bootstrap_gstreamer(False)
+        return installed_something
 
     def _platform_bootstrap_gstreamer(self, force: bool) -> bool:
         if not force and self.is_gstreamer_installed(cross_compilation_target=None):