GHC saves the llvm command name (llc, opt, clang) found at compile time in its
settings file.
Using BINARY_ALIAS allows lang/ghc to build but breaks
ghc ports (devel/hs-cabal-install for example)
GHC configure script accepts now to define LLC, OPT, CLANG as
environment variable, switch to it.
<no location info>: error:
Warning: Couldn't figure out LLVM version!
Make sure you have installed LLVM 9
<no location info>: error: ghc: could not execute: opt-9.0
PR: 252166, 253367
Approved by: portmgr (tier-2 blanket)
Mikael Urankar
143fad9226