Set BFD_DECOMPRESS to decompress debug sections

Set BFD_DECOMPRESS to decompress debug sections

We should set BFD_DECOMPRESS to decompress debug sections when reading in
DWARF debug sections.

bfd/

	PR binutils/19523
	* dwarf2.c (_bfd_dwarf2_slurp_debug_info): Set BFD_DECOMPRESS to
	decompress debug sections.

binutils/

	PR binutils/19523
	* Makefile.am (check-DEJAGNU): Pass CC and CC_FOR_BUILD to
	runtest.
	* Makefile.in: Regenerated.
	* testsuite/binutils-all/compress.exp (test_gnu_debuglink): New
	proc.
	Run test_gnu_debuglink for native ELF build.