Use folder-relative output folder in the XPLAINBridge makefile.

Projects/XPLAINBridge/makefile

@@ -34,8 +34,8 @@ all:
 # Since this project borrows files from the AVRISP-MKII project which may also have an
 # identical OBJDIR directory, we need to enforce the use of this project's object file
 # directory as the one where the build object files are to be stored, by giving it a
-# project-specific name.
-OBJDIR      := obj.$(TARGET)
+# path relative to the current folder.
+OBJDIR      := ./obj
 
 # Include LUFA-specific DMBS extension modules
 DMBS_LUFA_PATH ?= $(LUFA_PATH)/Build/LUFA