vbox: Provide implementation of RTErrCOMGet

The generated errmsgvboxcomdata.h is currently empty, but the
'main.e.l.f' log group seems to work for now.

repos/ports/lib/mk/virtualbox-runtime.mk

@@ -156,3 +156,8 @@ errmsgdata.h: $(VIRTUALBOX_DIR)/include/iprt/err.h \
 	$(MSG_CONVERT)$@
 	$(VERBOSE)sed -f $(VBOX_DIR)/Runtime/common/err/errmsg.sed $^ > $@
 
+SRC_CC += Runtime/common/err/errmsgxpcom.cpp
+Runtime/common/err/errmsgxpcom.o: errmsgvboxcomdata.h
+
+errmsgvboxcomdata.h:
+	touch $@

repos/ports/src/virtualbox/unimpl.cc

@@ -24,8 +24,6 @@ void name(void) { \
 	while (1) { Assert(!"not implemented"); } \
 }
 
-DUMMY(RTErrCOMGet)
-
 DUMMY(DBGFR3CoreWrite)
 DUMMY(DBGCRegisterCommands)
 DUMMY(DBGFR3EventAssertion)