message: guix: use Clang 10 for the macOS cross compile
diff: @@ -239,5 +239,5 @@ chain for " target " development."))
  ((string-contains target "-linux-")
  (list (make-bitcoin-cross-toolchain target)))
  ((string-contains target "darwin")
  - (list clang-toolchain-8 binutils imagemagick libtiff librsvg font-tuffy cmake xorriso))
  + (list clang-toolchain-10 binutils imagemagick libtiff librsvg font-tuffy cmake xorriso))
  (else '())))))
  