Display output of java stderr stream

[polarstoat]

spigot-updater/update.command

Line 47 in 76ab62f

java -Xmx2G -jar BuildTools.jar > /dev/null 2>&1 || fatal_error 'Build failed'

The BuildTools.jar script outputs a lot of messages, which can be intimidating for users who are not familiar with the shell.

Currently Spigot updater hides all of the stdout and stderr from BuildTools.jar by redirecting the output to /dev/null, but in the case of the build process failing no specific information is provided to the user.

Instead, the BuildTools.jar stdout and stderr should be examined to determine if there is any/useful information sent to stderr, and if so Spigot updater should display that information, only redirecting stdout to /dev/null.