multimedia/libbluray: Fix environment variable conflict with portmaster

libbluray (> 1.0.2,1) uses the PACKAGES variable in its configure scripts
that contains the names of packages it depends on. Portmaster also uses the
PACKAGES environment variable.

Using portmaster to install libbluray results in a corrupted libbluray
pkgconfig file containing portmasters PACKAGES path:

Requires.private: /usr/home/koobs/repos/freebsd/ports/packages libxml-2.0 freetype2 fontconfig

This breaks libbluray consumers such as ffmpeg.

This change nulls out the PACKAGES variable during the configure stage of
the build to prevent the issue. [1]

While I'm here,

• Sort JAVA_* and USE_* entries.

PR: 226009
Reported by: Martin Birgmeier <d8zNeCFG aon at> [1]
Submitted by: VVD <vvd unislabs com> [1]
Approved by: portmgr (unmaintained port)
MFH: 2019Q2 (blanket: runtime bugfix)