Prefer executable in JAVA_HOME when defined

[AlexFalappa]

It would be great to prefer the java executable found in a user explicitly defined JAVA_HOME.

I had an issue on a centrally managed Windows 10 system where an Oracle JRE 8 was defined in the system path and I couldn't override it by redefining the PATH in the local user account environment variables definition, this prevented execution of maven javafx:run for example with missing --modulepath error.

At the moment a java is found in the system executable path is chosen, the following two blocks should be flipped:

javafx-maven-plugin/src/main/java/org/openjfx/JavaFXBaseMojo.java

Lines 360 to 371 in 17b219c

	if (exec == null && OS.isFamilyWindows()) {
	List<String> paths = this.getExecutablePaths(enviro);
	paths.add(0, dir.getAbsolutePath());
	exec = findExecutable(executable, paths);
	}
	if (exec == null) {
	String javaHome = System.getProperty("java.home", getJavaHome(enviro));
	if (javaHome != null && ! javaHome.isEmpty()) {
	exec = findExecutable(executable, Arrays.asList(javaHome.concat(File.separator).concat("bin")));
	}
	}