Auto merge of #10617 - perlun:extract-build-properties-script-to-py-files, r=bholley

Extracted Mako-based code generation invokation to separate .py files.

This breaks out some of the parts on #10586, that should be easily mergeable (hopefully pretty much a no-brainer really). The idea would be to let you review & merge it first, and then I'll complete the other PR rebase off of this stuff.

@bholley - I did like you suggested and broke it out for `geckolib` as well. The tests should also be running without problems (tested `./mach test-unit` locally).

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components/style/build.rs

@@ -43,19 +43,7 @@ fn main() {
         .env("PYTHONPATH", &mako)
         .env("TEMPLATE", &template)
         .env("PRODUCT", product)
-        .arg("-c")
-        .arg(r#"
-import os
-import sys
-from mako.template import Template
-from mako import exceptions
-try:
-    template = Template(open(os.environ['TEMPLATE'], 'rb').read(), input_encoding='utf8')
-    print(template.render(PRODUCT=os.environ['PRODUCT']).encode('utf8'))
-except:
-    sys.stderr.write(exceptions.text_error_template().render().encode('utf8'))
-    sys.exit(1)
-"#)
+        .arg("generate_properties_rs.py")
         .stderr(Stdio::inherit())
         .output()
         .unwrap();

components/style/generate_properties_rs.py

@@ -0,0 +1,17 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+import os
+import sys
+
+from mako import exceptions
+from mako.template import Template
+
+try:
+    template = Template(open(os.environ['TEMPLATE'], 'rb').read(),
+                        input_encoding='utf8')
+    print(template.render(PRODUCT=os.environ['PRODUCT']).encode('utf8'))
+except:
+    sys.stderr.write(exceptions.text_error_template().render().encode('utf8'))
+    sys.exit(1)