More information in requirements error message

Followup to PR #624:

- For some reason we determined in issue #623 & PR #624 that logging the value of JAVA_HOME was misleading. Part of the explanation may be that check_reqs.js overwrites the setting which I think is not the best solution. I would favor that we look for a better solution, then log the actual JAVA_HOME setting in case there was an issue with Java.
- Looking at the changes in PR #624, I think it would be ideal if the code would make it clear if there is an issue with both Java and Android SDK.

Start with check_reqs.js and review the context in issue #623 and PR #624. Trace how JAVA_HOME and the Java and Android SDK checks are handled, then verify that the requirements error message reports the actual relevant setting and distinguishes Java problems from Android SDK problems.

Written by the indexing model from the issue text.