tools: update gyp-next to v0.6.0
Refs: https://github.com/nodejs/gyp-next/releases/tag/v0.6.0
Checklist
-
make -j4 test
(UNIX), orvcbuild test
(Windows) passes -
tests and/or benchmarks are included -
documentation is changed or added -
commit message follows commit guidelines
/cc @MylesBorins @rvagg @targos