[libcxx-dev] Problem installing libcxx and libcxxabi using Bootstrapping on Amazon Linux 2

[Raul Tambre via libcxx-dev]

CMake would search /usr/local prefix by default, but alas plv8 seems to use 
Makefiles. Sticking "-L/usr/local/lib/x86_64-unknown-linux" here 
(<https://github.com/plv8/plv8/blob/r3.1alpha/Makefile#L166>) might be 
sufficient. It might be easier to simply use libstdc++ though.