build: fix JDK_HOME variable handling.
build: fix JDK_HOME variable handling.

Declare the variable precious (so that it's saved) and document it,
instead of adding a --with-jdk and then use the variable.

koying/libbluray,ace20022/libbluray,vlc-mirror/libbluray,UIKit0/libbluray,ShiftMediaProject/libbluray,koying/libbluray,UIKit0/libbluray,zxlooong/libbluray,EdwardNewK/libbluray,mwgoldsmith/bluray,UIKit0/libbluray,UIKit0/libbluray,mwgoldsmith/bluray,EdwardNewK/libbluray,ace20022/libbluray,pingflood/libbluray,ace20022/libbluray,ShiftMediaProject/libbluray,Distrotech/libbluray,Distrotech/libbluray,koying/libbluray,tourettes/libbluray,ace20022/libbluray,Azzuro/libbluray,EdwardNewK/libbluray,Azzuro/libbluray,EdwardNewK/libbluray,vlc-mirror/libbluray,mwgoldsmith/bluray,vlc-mirror/libbluray,zxlooong/libbluray,Distrotech/libbluray,pingflood/libbluray,ShiftMediaProject/libbluray,koying/libbluray,Azzuro/libbluray,pingflood/libbluray,zxlooong/libbluray,vlc-mirror/libbluray,Distrotech/libbluray,tourettes/libbluray,mwgoldsmith/bluray,Azzuro/libbluray,ShiftMediaProject/libbluray,tourettes/libbluray,tourettes/libbluray