build scripts: adding support for building externs in the Implementations/Max submodule.
build scripts: adding support for building externs in the Implementations/Max submodule.

eriser/JamomaCore,eriser/JamomaCore,jamoma/JamomaCore,eriser/JamomaCore,eriser/JamomaCore,jamoma/JamomaCore,jamoma/JamomaCore,jamoma/JamomaCore,jamoma/JamomaCore,jamoma/JamomaCore,jamoma/JamomaCore,eriser/JamomaCore,eriser/JamomaCore,eriser/JamomaCore,eriser/JamomaCore