Make builds able to depend on external projects (#291)

* Make builds able to depend on external projects

Builds are now able to load external projects and depend on them
as if they were local submodules.

`import $file.external.path.build`

* Disambiguate "dest" for foreign modules.

* Calling modules loaded from external directories "Foreign" to avoid
conflicting with the already existing concept of "ExternalModule".
* Amended the way `dest` is computed for foreign modules
* Added tests to check that the source paths and dest are as expected
* Added a test to show that local modules do not conflict with foreign
modules when they are named the same

* WIP windows build fail

* Added bootstrapping step in CYGWIN CI job

* * Revert externalOutPath deletion
* Add documentation for foreign-modules

* reverting appveyor changes

* Disabling Foreign modules tests against Java9

See https://github.com/lihaoyi/mill/issues/302

1 files changed, 1 insertions, 1 deletions

diff --git a/scalalib/src/mill/scalalib/PublishModule.scala b/scalalib/src/mill/scalalib/PublishModule.scala
index 2ab81269..9626f1c2 100644
--- a/scalalib/src/mill/scalalib/PublishModule.scala
+++ b/scalalib/src/mill/scalalib/PublishModule.scala
@@ -118,4 +118,4 @@ object PublishModule extends ExternalModule{
   implicit def millScoptTargetReads[T] = new mill.main.Tasks.Scopt[T]()
 
   lazy val millDiscover: mill.define.Discover[this.type] = mill.define.Discover[this.type]
-}
\ No newline at end of file
+}