LLVM test Transforms/InferFunctionAttrs/annotate contains two RUN
invokation (UNKNOWN and NVPTX lines) which involve a CHECK-NOT directive
with a variable not defined by the enabled CHECK prefixes. This commit
fixes that by:
- enabling CHECK prefix for unknown target with specialisation when it
differs from other targets
- checking for absence of bcmp with any attribute for NVPTX
Reviewed By: tra
Differential Revision: https://reviews.llvm.org/D99589