crate_hash -> cgu_hash and don't hash the crate hash.

[vext01]

The crate hash changes frequently (with every source code change), so we shouldn't use it in the CGU hash.

There is a companion commit coming for this and we will need to do a cycle breaker.

Companion: https://github.com/softdevteam/yk/pull/113

[bjorn3]

bors try

[bors[bot]]

try

Build failed:

• buildbot/ykrustc-buildbot-build-script-hwt

[vext01]

That'll fail due to the path override. Once we've reviewed both PRs, I'll add a cycle breaker.

[vext01]

Cycle breaker in place.

bors try

[bors[bot]]

try

Build succeeded:

• buildbot/ykrustc-buildbot-build-script-hwt

[bjorn3]

softdevteam/yk#113 has been merged.

[vext01]

Removed cycle breaker and updated lock in a force push.

[bjorn3]

bors r+

[bors[bot]]

Build succeeded:

• buildbot/ykrustc-buildbot-build-script-hwt