[rush] `rush-pnpm approve-builds` should update `common/config/rush/pnpm-config.json`

[kgetz-arista]

Summary

rush-pnpm approve-builds does not update common/config/rush/pnpm-config.json, which means the user is presented with the same warning on every rush update.

Repro steps

1. Upgrade to the latest version of Node and pnpm
2. Run rush update in a repo where dependencies have build scripts
3. See the warning about "Ignored build scripts"
4. Run rush-pnpm approve-builds and approve the dependencies
5. Run rush update again
6. See that the warning still appears

Expected result: Warning should go away

Actual result: Warning continues to appear

Details

See #5542 also.

Standard questions

Please answer these questions to help us investigate your issue more quickly:

Question	Answer
@microsoft/rush globally installed version?	5.165.0
rushVersion from rush.json?	5.165.0
pnpmVersion, npmVersion, or yarnVersion from rush.json?	pnpm@10.27.0
(if pnpm) useWorkspaces from pnpm-config.json?	true
Operating system?	Windows 11
Would you consider contributing a PR?	No
Node.js version (node -v)?	24.12.0