setup script improvements, automatically clone xmrig-hac and build for multiple platforms

scripts/fetch-libsodium.sh

@@ -77,7 +77,7 @@ case "$TARGET" in
     mac)
         # Cross-compile for macOS via osxcross
         if [[ -z "${OSXCROSS:-}" ]]; then
-            for try in "$HOME/osxcross" "/opt/osxcross" "$PROJECT_DIR/osxcross"; do
+            for try in "$PROJECT_DIR/external/osxcross" "$HOME/osxcross" "/opt/osxcross" "$PROJECT_DIR/osxcross"; do
                 [[ -d "$try/target" ]] && OSXCROSS="$try" && break
             done
         fi