In the platform-specific defines, instead of declaring ADB_OUT_DIR, specify the files to copy, i.e. for Windows:

    ADB_LIBS = \
      android-tools/win-out/libadb$(LIB_SUFFIX) \
      $(ADB_DRIVERS_DIR)api/objfre_wxp_x86/i386/AdbWinApi$(LIB_SUFFIX) \
      $(ADB_DRIVERS_DIR)winusb/objfre_wxp_x86/i386/AdbWinUsbApi$(LIB_SUFFIX)

And for Mac/Linux:

    ADB_LIBS = android-tools/adb-bin/libadb$(LIB_SUFFIX)

Then you can copy those files to DATA_ADB_PATH without having to write platform-specific code in the recipe:

    make -C android-tools lib && \
    make -C android-tools driver && \
    cp $(ADB_LIBS) $(DATA_ADB_PATH);