Add jvm-ce-ntl build configuration

* jvm-ce but with native toolchain launchers to build C extensions faster.

Author: eregon

doc/contributor/workflow.md

@@ -125,14 +125,17 @@ This warning is important.
 
 ### Building C Extensions more quickly
 
-To speed up compilation of bundled C extensions, it is possible to use
-*native* toolchain launchers, which might save some build time.
-See the [related documentation](https://github.com/oracle/graal/blob/master/sulong/docs/contributor/TOOLCHAIN.md#using-a-prebuilt-graalvm-as-a-bootstrapping-toolchain)
-in Sulong to build and use them.
-
-You can also use `export JT_CACHE_TOOLCHAIN=true` to have the native toolchain
-launchers built and used by `jt` automatically. `jt` will keep the 4 newest
-built toolchain launchers to avoid rebuilding when branches are switched.
+Speeding up compilation of C extensions can be achieved by using *native* toolchain launchers,
+instead of the Bash toolchain launchers used with the `jvm*` build configurations.
+
+For bundled C extensions (that is, extensions under `src/main/c`),
+you can `export JT_CACHE_TOOLCHAIN=true` and that will then use native toolchain launchers for the
+[bootstrap toolchain](https://github.com/oracle/graal/blob/master/sulong/docs/contributor/TOOLCHAIN.md#using-a-prebuilt-graalvm-as-a-bootstrapping-toolchain).
+This has no effect after `jt build`.
+
+For C extensions installed after `jt build` by e.g. `gem install` or `bundle install`,
+one can use the `jvm-ce-ntl` build configuration which includes *native* toolchain launchers,
+or use one of the `native*` build configuration (which also builds a native truffleruby launcher).
 
 ## Editors and IDEs
 

mx.truffleruby/jvm-ce-ntl

@@ -0,0 +1,5 @@
+# "ntl" stands for native toolchain launchers
+DYNAMIC_IMPORTS=/substratevm,/tools
+COMPONENTS=TruffleRuby,SubstrateVM,suite:tools
+FORCE_BASH_LAUNCHERS=truffleruby
+DISABLE_INSTALLABLES=false