Do not recommend building with binary suites

PullRequest: truffleruby/667

Author: eregon

.gitignore

@@ -68,7 +68,6 @@ test/mri/tests/cext-c/**/*.o
 /mx.truffleruby/env
 /mx.truffleruby/eclipse-launches
 /mxbuild
-/mx.imports
 /TRUFFLERUBY*.dist
 
 # ruby/spec

doc/contributor/workflow.md

@@ -49,13 +49,6 @@ jt mx version
 
 ## Building
 
-We recommend configuring the build to use the Truffle framework as a binary
-dependency rather than importing it as source code.
-
-```bash
-$ echo MX_BINARY_SUITES=tools,truffle,sdk > mx.truffleruby/env
-```
-
 ```bash
 $ jt build
 ```

mx.truffleruby/suite.py

@@ -102,7 +102,6 @@
                 "dumps",
                 "logo",
                 "mxbuild",
-                "mx.imports",
                 ".ext",
                 "truffleruby-gem-test-pack",
                 "lib/json/java",