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

[David DeHaven]

I can't comment on non-Oracle JDKs, but It's in libjli so anything based on OpenJDK should support it.

-DrD-

> I was not aware of the existence of the -fullversion option. It is not listed at the Oracle site, afaik. Can it be assumed to be present in non-OpenJDK, non-Oracle JDKs?
> 
> David DeHaven schreef op 2015-08-26 15:38:
>>> 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-
>