lang/openjdk8: Set IGNORE_CCCACHE=

openjdk has a scheme to figure out if the compiler is gcc or clang.
While it tries to see through ccache, using
  PKGSRC_COMPILER=ccache gcc
fails.  Set IGNORE_CCCACHE=yes as documented in mk/compiler/ccache.mk
to avoid using ccache, until someone fixes this better.

(gdt)