RFR: JDK-8244210: The javac server is never used

[Florian Weimer]

* Erik Joelsson:

> A minor mistake in JDK-8244036 is causing the javac server to never be 
> used, which is rather severly increasing build times.
>
> Before that change, the global variable ENABLE_SJAVAC was used to 
> determine if the server should be activated. After the change, the 
> global variable has changed names to ENABLE_JAVAC_SERVER. The 
> conditional in JavaCompilation.gmk tries to check the value of the local 
> variable/parameter $1_ENABLE_JAVAC_SERVER instead, but this parameter is 
> never set or given a default. I don't think we need a local 
> variable/parameter for this as there is currently no need to disable the 
> server for any specific SetupJavaCompilation call, so I my fix is to 
> just refer directly to the global variable from configure/spec.gmk instead.
>
> Bug: https://bugs.openjdk.java.net/browse/JDK-8244210
>
> Webrev: http://cr.openjdk.java.net/~erikj/8244210/webrev.01/webrev/

I'm happy to report that this brings back the build times to normal.