pkg/53083: devel/gradle package hard-codes JAVA_HOME

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>Number:         53083
>Category:       pkg
>Synopsis:       devel/gradle package hard-codes JAVA_HOME
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    pkg-manager
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Thu Mar 08 20:00:00 +0000 2018
>Originator:     Nathan Arthur
>Release:        pkgsrc-current
>Organization:
>Environment:
Darwin narthur-pro.preemptive.internal 17.4.0 Darwin Kernel Version 17.4.0: Sun Dec 17 09:19:54 PST 2017; root:xnu-4570.41.2~1/RELEASE_X86_64 x86_64

>Description:
The `gradle-launcher` script included with devel/gradle is installed as the `gradle` command. That script has the following line:

JAVA_HOME="@JAVA_HOME@"

The effect of this is that all runs of the `gradle` command will end up using the Java version that was configured at build time (and for precompiled packages, on the build server). This breaks longstanding gradle behavior where it observes/obeys the JAVA_HOME set in the environment.
>How-To-Repeat:
Configure JAVA_HOME
Build and install devel/gradle
Change JAVA_HOME to point somewhere else
Run `gradle`
Observe that it uses the wrong Java version
>Fix:
A suggested fix:

JAVA_HOME="${JAVA_HOME:-@JAVA_HOME@}"