Manual backport of #15274 to <= 3-0-x

Notes: fix Electron not being visible when launching in development mode on node v11

Release builds should be run before branch builds on our limited macOS
infra.

Refs: https://docs.microsoft.com/en-us/rest/api/vsts/build/builds/queue?view=vsts-rest-4.1#queuepriority

* fix: make release-artifact-cleanup executable

* fix misc issues in cleanup script

* Fix Accelerator Flags for Windows and Linux

* Lint fix

* Lint whitespace

Merge pull request #14700 from trop-bot/1-8-x-bp-ci--skip-vsts-testing-builds-on-older-branches-1537376182355

ci: Skip VSTS testing builds on older branches (backport: 1-8-x)

Also, don't send slack notifications for actual releases

I want to clean up this "stable" and "beta" code smell eventually but
for now this will unblock the 2.0.x releases.

ci: don't run gn debug build on older branches (1-8-x)

* ci: don't run gn debug build on older branches

Older branches that build using gyp do not run both a debug and testing build.

* Actually skip the build if debug

(cherry picked from commit f924a160)
(cherry picked from commit 5f3bedd1)

Release the view of status item before destroying it,
gives chance to perform cleanup on the view.

chore: backport release script updates to 1-8-x

ci: Rename appveyor-override to appveyor (1-8-x)

Make sure we have consistent names on our CI config files.

Picks up electron/libchromiumcontent#638

Merge pull request #13610 from trop-bot/1-8-x-bp-ci--use-visual-studio-2015-for-2-0-x-and-older-1531233806214

Backport (1-8-x) - ci: Use Visual Studio 2015 for 2-0-x and older

https://chromium-review.googlesource.com/677290

update libcc submodule reference to electron-1-8-x

remove appveyor.yml to fix windows CI builds

Merge pull request #12962 from trop-bot/1-8-x-bp-fix-empty-description-when-only-one-extension-is-given-(getfiletypesfromaccepttype)-1526480225772

Backport (1-8-x) - Fix empty description when only one extension is given (GetFileTypesFromAcceptType)