testsuite option to skip cilkplus?

[Tim Prince <tprince818.tp@xxxxxxxxx>]

gcc trunk testsuite attempts to test cilkplus on WSL regardless of 
setting --disable-libcilkrts (which does stop the attempted build of 
libcilkrts).  Shouldn't there be a way to suppress these tests for 
targets where cilkplus is not supported?  At last count, 116 FAIL 
reports (and some PASS) are associated with cilk-plus.

I began to post bugzilla reports about cilkplus reducer bugs a year ago, 
but they still sit in NEW status.  Recently, I began seeing news that 
cilkplus should be removed from gcc8.