Remove -Xmx512M flag when detecting java version
Remove -Xmx512M flag when detecting java version

The flag can cause problems when there is another configuration
adding -Xms with a value bigger than 512M. The `java -version`
command will fail and no java version will be detected, causing
a failure in `checkJava`.

sbt/sbt,xuwei-k/xsbt,mdedetrich/sbt,xuwei-k/xsbt,sbt/sbt-launcher-package,mdedetrich/sbt,xuwei-k/xsbt,xuwei-k/xsbt,sbt/sbt,mdedetrich/sbt,sbt/sbt,xuwei-k/xsbt,mdedetrich/sbt,sbt/sbt-launcher-package,sbt/sbt,sbt/sbt,mdedetrich/sbt,mdedetrich/sbt,sbt/sbt,sbt/sbt,mdedetrich/sbt