message: guix: only download sources for hosts being built
  If a user is only interested in building for Linux, this saves
  downloading the macOS compiler and additional dependencies.
  This will result in a few additional `make` invocations, for the Linux
  hosts, however this is quite low overhead.
diff: @@ -136,9 +136,24 @@ done
  # environment)
  MAX_JOBS="${MAX_JOBS:-$(nproc)}"
  +# Usage: host_to_commonname HOST
  +#
  +# HOST: The current platform triple we're building for
  +#
  +host_to_commonname() {
  + case "$1" in
  + *darwin*) echo osx ;;
  + *mingw*) echo win ;;
  + *linux*) echo linux ;;
  + *) exit 1 ;;
  + esac
  +}
  +
  # Download the depends sources now as we won't have internet access in the build
  # container
  -make -C "${PWD}/depends" -j"$MAX_JOBS" download ${V:+V=1} ${SOURCES_PATH:+SOURCES_PATH="$SOURCES_PATH"}
  +for host in $HOSTS; do
  + make -C "${PWD}/depends" -j"$MAX_JOBS" download-"$(host_to_commonname "$host")" ${V:+V=1} ${SOURCES_PATH:+SOURCES_PATH="$SOURCES_PATH"}
  +done
  # Determine the reference time used for determinism (overridable by environment)
  SOURCE_DATE_EPOCH="${SOURCE_DATE_EPOCH:-$(git log --format=%at -1)}"
  