bpf: do not --enable-gcov for bpf-*-* targets

This patch changes the build machinery in order to disable the build
of GCOV (both compiler and libgcc) in bpf-*-* targets.  The reason for
this change is that BPF is (currently) too restricted in order to
support the coverage instrumentalization.

Tested in bpf-unknown-none and x86_64-linux-gnu targets.

2022-02-23  Jose E. Marchesi  <jose.marchesi@oracle.com>

gcc/ChangeLog

	PR target/104656
	* configure.ac: --disable-gcov if targetting bpf-*.
	* configure: Regenerate.

libgcc/ChangeLog

	PR target/104656
	* configure.ac: --disable-gcov if targetting bpf-*.
	* configure: Regenerate.