As described in #2336, I noticed that when using 0.13 nightly from
Bintray, sbt was unable to locate the compiler source.
Since `updateSbtClassifiers` is already set up to download sbt's own
sources, the `ivyConfiguration` should be reused. However, `compilers`
is a derived task, which is unable to depend on a scoped key.
To workaround this I had to create a new key called
`bootIvyConfiguration`. This should now use the metabuild's resolvers
to download the compiler bridge source.
Adds a new setting `useJCenter`, which is set to `false` by default.
When set to `true`, JCenter will be placed as the first external
resolver to find library dependencies.
The implementation of `externalResolvers` is changed to incorporate the
setting by calling `Resolver.reorganizeAppResolvers`. These changes
were required because `externalResolvers` uses whatever that's in the
launchconfig, which the build user may not upgrade.
Eugene Yokota