java/openjdk8: add support for powerpc64le

powerpc64le needs --disable-jfr and USE_PRECOMPILED_HEADER=0 - same as powerpc64 elfv2.

Clang refuses to build little-endian binaries for power7, this needs to be bumped to power8 (this is a bug in openjdk, POWER7 is not LE-compatible).

-minsert-sched-nops=regroup_exact -mno-multiple -mno-string are not supported by clang and need to be removed.

FreeBSD uses sys/endian.h instead of byteswap.h and bswap{16,32,64} instead of bswap_{16,32,64}.

PR: 251247
Approved by: java (maintainer timeout)