fix: generate breakpad symbols before stripping

[nornagon]

Description of Change

Looks like at some point we switched the order of strip and generate symbols, meaning we have been producing near-useless Linux symbols for some time now. (Afaict the symbols for Electron v5 are OK, but the v6 ones are broken.)

Checklist

• PR description included and stakeholders cc'd
• npm test passes
• tests are changed or added
• relevant documentation is changed or added
• PR title follows semantic commit guidelines
• PR release notes describe the change in a way relevant to app developers, and are capitalized, punctuated, and past tense.

Release Notes

Notes: Fixed debug symbol files on linux not containing private symbols.

[jkleinsc]

Release builds here:
CircleCI release build request for linux-arm64-publish successful. Check https://circleci.com/gh/electron/electron/353712 for status.
CircleCI release build request for linux-x64-publish successful. Check https://circleci.com/gh/electron/electron/353715 for status.
CircleCI release build request for linux-arm-publish successful. Check https://circleci.com/gh/electron/electron/353711 for status.
CircleCI release build request for mas-publish successful. Check https://circleci.com/gh/electron/electron/353716 for status.
CircleCI release build request for osx-publish successful. Check https://circleci.com/gh/electron/electron/353714 for status.
CircleCI release build request for linux-ia32-publish successful. Check https://circleci.com/gh/electron/electron/353713 for status.

[jkleinsc]

Release builds running here:
CircleCI release build request for linux-ia32-publish successful. Check https://circleci.com/gh/electron/electron/354516 for status.
CircleCI release build request for mas-publish successful. Check https://circleci.com/gh/electron/electron/354514 for status.
CircleCI release build request for linux-arm64-publish successful. Check https://circleci.com/gh/electron/electron/354517 for status.
CircleCI release build request for linux-arm-publish successful. Check https://circleci.com/gh/electron/electron/354515 for status.
CircleCI release build request for osx-publish successful. Check https://circleci.com/gh/electron/electron/354518 for status.
CircleCI release build request for linux-x64-publish successful. Check https://circleci.com/gh/electron/electron/354519 for status.

[nornagon]

Seems to be working—the symbol files are now ~80MB instead of ~800KB.

[jkleinsc]

Merging as CI failures unrelated to change.

[release-clerk]

Release Notes Persisted

Fixed debug symbol files on linux not containing private symbols.