Don't run tests requiring "B" on designs without "B"

Don't run tests requiring "B" on designs without "B"

So I resurrected our milkv pioneer over the weekend.  While we had the
tell-tale signs of PCIE switch issues, it actually appears that the NMVE drive
was failing.  I had an NVME that was going to be installed in a different
system, so I threw it into the Pioneer as a last ditch effort to get it
functional again.  Voila!  It's a happy camper (so far).

Naturally I don't like manual testing, so cobbled together a new target for my
tester.  I forgot to update one field when doing that and as a result it picked
up testsuite prior test results from the job that runs on the BPI.

So comparing test results from a BPI to the Pioneer wouldn't normally be
interesting.  We'd expect to see a whole bunch of tests disappear as the
Pioneer doesn't have all kinds of extensions that the BPI does (and that does
indeed happen).

As it turns out we have a handful of tests which need bitmanip to run, but
which don't restrict themselves to only run on appropriate hardware.  So we
might as well fix that.

Given the Pioneer/BPI take 6/24 hours to cycle through respectively I just spot
checked the testsuite changes. Pushing to the trunk.

gcc/
	* doc/sourcebuild.texi: Add riscv_b_ok and riscv_v_ok target selectors.

gcc/testsuite/
	* lib/target-supports.exp (check_effective_target_riscv_b_ok): New.
	* gcc.target/riscv/pr116085.c: Use new target selector.
	* gcc.target/riscv/pr117690.c: Use new target selector.
	* gcc.target/riscv/pr120333.c: Use new target selector.
	* gcc.target/riscv/zba-shNadd-10.c: Use new target selector.