The interaction of some JVMCI flags is suboptimal. For example, the help for UseJVMCINativeLibrary says it defaults to true if EnableJVMCIProduct is true but EnableJVMCIProduct is a macro flag and the implementation actually checks UseJVMCICompiler. There are also a number of places in the code guarded by UseJVMCICompiler that should instead be guarded by EnableJVMCI. JDK-8340398 is fixing one such instance of this but there's almost certainly other places that needed to be fixed up.

As background, the motiviating use case of `-XX:+EnableJVMCI -XX:-UseJVMCICompiler` is Truffle when the user wants to use C2 for CompilerBroker JIT compilations but still use Graal for Truffle partial-evaluation compilations.