Proposed fix: buildscript java version detection fails on Linux/Ubuntu on Picked up JAVA_TOOL_OPTIONS

[David DeHaven]

> The gradle build tries to find the version of the used Java JDK by running 'java -version', skipping the first line and expects to find the version in the second line.
> 
> However, on Linux (Ubuntu) the first line of *any* Java invocation is "Picked up JAVA_TOOL_OPTIONS: -javaagent:/usr/share/java/jayatanaag.jar"[1], thus failing at detection of the version, aborting the build.
> 
> The 'Pickup up...' line is a standard feature of the JDK and a legacy that doesn't seem to be removed soon[2].
> 
> I guess the build script needs to accommodate for this.
> 
> Proposed fix:
> 
> // Determine the verion of Java in JDK_HOME. It looks like this:
> //
> // $ java -version
> // Picked up JAVA_TOOL_OPTIONS: -javaagent:/usr/share/java/jayatanaag.jar
> // java version "1.7.0_45"
> // Java(TM) SE Runtime Environment (build 1.7.0_45-b18)
> // Java HotSpot(TM) 64-Bit Server VM (build 24.45-b08, mixed mode)
> //
> // The first line is optional, we need to parse the third line
> def inStream = new java.io.BufferedReader(new java.io.InputStreamReader(new java.lang.ProcessBuilder(JAVA, "-version").start().getErrorStream()));
> try {
>    String v = inStream.readLine();
> 
>    if (v != null) {
> 	if (v.startsWith("Picked up")) {
> 	   inStream.readLine();
> 	}
> 
>        v = inStream.readLine();

Why not just use "java -fullversion" instead?

$ java -fullversion
java full version "1.8.0_60-ea-b14"

$ JAVA_TOOL_OPTIONS="-Xmx512M" java -fullversion
java full version "1.8.0_60-ea-b14"

$ java -version
java version "1.8.0_60-ea"
Java(TM) SE Runtime Environment (build 1.8.0_60-ea-b14)
Java HotSpot(TM) 64-Bit Server VM (build 25.60-b14, mixed mode)

$ JAVA_TOOL_OPTIONS="-Xmx512M" java -version
Picked up JAVA_TOOL_OPTIONS: -Xmx512M
java version "1.8.0_60-ea"
Java(TM) SE Runtime Environment (build 1.8.0_60-ea-b14)
Java HotSpot(TM) 64-Bit Server VM (build 25.60-b14, mixed mode)

It's a lot less stuff to parse. Also, "java -fullversion" does not start the VM, so should be faster.

-DrD-