sagemathgh-37671: pkgs/sagemath-standard: Support gpep517
    
From sagemath#37138 (comment)

<!-- ^ Please provide a concise and informative title. -->
<!-- ^ Don't put issue numbers in the title, do this in the PR
description below. -->
<!-- ^ For example, instead of "Fixes sagemath#12345" use "Introduce new method
to calculate 1 + 2". -->
<!-- v Describe your changes below in detail. -->
<!-- v Why is this change required? What problem does it solve? -->
<!-- v If this PR resolves an open issue, please link to it here. For
example, "Fixes sagemath#12345". -->

### 📝 Checklist

<!-- Put an `x` in all the boxes that apply. -->

- [x] The title is concise and informative.
- [ ] The description explains in detail what this PR is about.
- [x] I have linked a relevant issue or discussion.
- [ ] I have created tests covering the changes.
- [ ] I have updated the documentation accordingly.

### ⌛ Dependencies

<!-- List all open PRs that this PR logically depends on. For example,
-->
<!-- - sagemath#12345: short description why this is a dependency -->
<!-- - sagemath#34567: ... -->
    
URL: sagemath#37671
Reported by: Matthias Köppe
Reviewer(s): François Bissey

Author: Release Manager

pkgs/sagemath-standard/setup.py

@@ -64,7 +64,7 @@
 #########################################################
 
 if any(x in sys.argv
-       for x in ['build', 'bdist_wheel', 'install']):
+       for x in ['build', 'build_ext', 'bdist_wheel', 'install']):
     log.info("Generating auto-generated sources")
     from sage_setup.autogen import autogen_all
     autogen_all()