Stable backports (#8055)

* CI: Fix cargo cache (#7968)

* Fix cache

Blocking waiting for file lock on the registry index

* Only clean locked cargo cache on windows

* fixed ethstore sign (#8026)

* fix cache & snapcraft CI build (#8052)

after successful testing it is necessary to port in a ```beta``` and ```stable```

*  Add MCIP-6 Byzyantium transition to Musicoin spec (#7841)

* Add test chain spec for musicoin byzantium testnet

* Add MCIP-6 Byzyantium transition to Musicoin spec

* Update mcip6_byz.json

* ethcore: update musicoin byzantium block number

* ethcore: update musicoin byzantium block number

* ethcore: update musicoin bootnodes

* Update musicoin.json

* Update musicoin.json

* More bootnodes.

scripts/gitlab-build.sh

@@ -48,6 +48,12 @@ set_env_win () {
   echo "@ signtool sign /f "\%"1 /p "\%"2 /tr http://timestamp.comodoca.com /du https://parity.io "\%"3" > sign.cmd
 }
 build () {
+  if [[ "windows" = $IDENT ]]
+  then
+    # This is a nasty hack till we figure out the proper cargo caching strategy
+    echo "Remove index"
+    rm -rf cargo/registry/index/*.
+  fi
   echo "Build parity:"
   cargo build --target $PLATFORM --features final --release
   echo "Build evmbin:"