[FIXED JENKINS-18898] ToolInstallation.getHome may be null, and buildEnvVars must take that into account.
[JENKINS-18898] Comment.
Unclear what Run.getEnvironment is supposed to return after the build is complete.
In particular, SubversionSCM calls this during polling to substitute variables in e.g. repo URL.
Presumably in such a case node-specific variables such as ToolInstallation.home would be irrelevant.
But in general should this reflect the “current” computer (if any), or the computer on which the build ran?
Merge branch 'master' of github.com:jenkinsci/jenkins