fix(dmg-builder): exec python fail on Macos12.3

[bytemain]

close: #6767

[changeset-bot]

🦋 Changeset detected

Latest commit: afbda22

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 7 packages

Name	Type
dmg-builder	Patch
electron-builder	Patch
electron-builder-squirrel-windows	Patch
electron-forge-maker-appimage	Patch
electron-forge-maker-nsis-web	Patch
electron-forge-maker-nsis	Patch
electron-forge-maker-snap	Patch

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[mmaietta]

This change is causing all mac dmg tests to fail as it's trying to use python @ /usr/local/bin/python

FAIL  src/mac/dmgTest.ts (585.119 s)
  ✕ dmg (13943 ms)

  ● dmg

    Exit code: ENOENT. spawn /usr/local/bin/python
     ENOENT

      131 |           }
      132 |
    > 133 |           reject(new Error(message))
          |                  ^
      134 |         }
      135 |       }
      136 |     )

      at ../packages/builder-util/src/util.ts:133:18

Unfortunately, github actions doesn't have a MacOS 12 build machine yet otherwise I'd be running our tests on that.

[bytemain]

it seem that which python got a result: /usr/local/bin/python.

but why it does not exists

[bytemain]

it seem that I have fixed it.

the return value of exec func has a '\n' suffix.

[mmaietta]

Thank you for your contribution!

Seems the Docs automation is frozen, but the CI tests all passed. Merging now