XPDEV and SBBS_SRC macros does not include a trailing slash.

xtrn/sbl/GNUmakefile

@@ -15,14 +15,14 @@
 # Macros
 XSDK		=	../sdk
 ifndef XPDEV
- XPDEV		=	../../src/xpdev/
+ XPDEV		=	../../src/xpdev
 endif
 ifndef SBBS_SRC
- SBBS_SRC	:=	$(XPDEV)../sbbs3/
+ SBBS_SRC	:=	$(XPDEV)../sbbs3
 endif
 NEED_THREADS	:=	1
-include $(XPDEV)Common.gmake
-include $(SBBS_SRC)Common.gmake
+include $(XPDEV)/Common.gmake
+include $(SBBS_SRC)/Common.gmake
 
 ifeq ($(os),sunos)
  LDFLAGS	+=	-lsocket -lnsl -lrt