Jason Tedor 55683d89c4
Clarify how to set compiler and runtime JDKs (#29101)
This commit enhances the error messages reported when JAVA_HOME and
RUNTIME_JAVA_HOME are not correctly set to point towards the minimum
compiler and minimum runtime JDKs that are expected by the builds. The
previous error message would say:

Java 1.9 or above is required to build Elasticsearch

which is confusing if the user does have a JDK 9 installation and is
even the version that they have on their path yet they have JAVA_HOME
pointing to another JDK installation. The error message reported after
this change is:

the environment variable JAVA_HOME must be set to a JDK installation directory for Java 1.9 but is [/usr/java/jdk-8] corresponding to [1.8]
2018-03-15 20:58:37 -04:00
..