* build: determine electron version from tags not files
* build: make electron_version dependent on packed-refs and git HEAD
* build: do not delete electron/.git
* build: do not revert a commit we didn't make
* build: gen version file instead of just writing it
* build: update cache and ninja targets
* build: copy resource.h to generated electron.rc
* build: electron_win32_resources should be public deps
* build: also copy the icon
