* 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