guix: Drop no longer needed PATH modification

contrib/guix/libexec/build.sh

@@ -230,8 +230,6 @@ case "$HOST" in
     *mingw*)  HOST_LDFLAGS="-Wl,--no-insert-timestamp" ;;
 esac
 
-# Make $HOST-specific native binaries from depends available in $PATH
-export PATH="${BASEPREFIX}/${HOST}/native/bin:${PATH}"
 mkdir -p "$DISTSRC"
 (
     cd "$DISTSRC"