Fedora Rawhide (will be Fedora 27) has moved to LLVM 4.0.0 and so Pony will not compile due to the LLVM version check.
You'd need to install 3.9.1
We do not currently support 4.0
OK, but Fedora is a "one and one only" type of system with regard to packaging, so I won't be able to build Pony on Fedora Rawhide till 4.0 is supported.
I notice that 3.9.0 is not acceptable but 3.9.1 is. Is it right that Pony depends on bug-fix version level?
Correct. There are bugs in 3.9.0 that were fixed in 3.9.1.
FYI, LLVMhas RPM packages available
I think we should close this in favor of #1592, where we are tracking efforts toward LLVM 4.0.x support
Reasonable.