chore: Allow fetching cross-platform parity-ethereum (#501)

* Allow fetching cross-platform

* Update ci

* Fix script
4 jobs for v0.3.0-beta in 8 minutes and 19 seconds (queued for 2 seconds)
latest
Status Job ID Name Coverage
  Test
passed #138202
linux-docker
linux-test

00:01:58

 
  Build
failed #138203
linux-docker
linux-build

00:06:21

failed #138204
darwin-shell
osx-build

00:04:43

failed #138205
linux-docker
win-build

00:04:11

 
Name Stage Failure
failed
win-build Build
No job log
failed
linux-build Build
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failed
osx-build Build
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