Bump version to 1.7.26

Merge branch 'master' into truffle-head

# Conflicts:
#	ci.hocon
#	truffle/src/main/java/org/jruby/truffle/language/DataNode.java

[Truffle] Do not use the build pack on truffle-head as it won't conta…

…in the latest truffle.

[Truffle] Don't change the environ in mx.

Merge branch 'master' into truffle-head

Doh...we don't want puts in our symlink impl

Update for release

Bump for 9.1.0.0