ld: add support for eBPF

ld: add support for eBPF

This patch adds support to the linker for the Linux eBPF architecture.
A minimal testsuite is included.

ld/ChangeLog:

2019-05-23  Jose E. Marchesi  <jose.marchesi@oracle.com>

	* Makefile.am (ALL_64_EMULATION_SOURCES): Add eelf64bpf.c.
	* Makefile.in (prefix): Regenerate.
	* configure.tgt (targ_extra_ofiles): Add case for bpf-*-* targets.
	* emulparams/elf64bpf.sh: New file.
	* testsuite/lib/ld-lib.exp (check_gc_sections_available): Add
	bpf-*-* to the list of targets not supporting gc-sections.
	* testsuite/ld-bpf/bar.s: New file.
	* testsuite/ld-bpf/jump-1.d: Likewise.
	* testsuite/ld-bpf/foo.s: Likewise.
	* testsuite/ld-bpf/call-1.d: Likewise.
	* testsuite/ld-bpf/bpf.exp: Likewise.
	* testsuite/ld-bpf/baz.s: Likewise.