dtspcd/dtterm: use proper DT_INCDIR rather than hardcoding the location

cde/programs/dtspcd/Makefile.am

@@ -4,7 +4,7 @@ bin_PROGRAMS = dtspcd
 
 dtspcd_CFLAGS = $(TIRPCINC) -DCDE_CONFIGURATION_TOP=\"${prefix}\" \
 		-DCDE_INSTALLATION_TOP=\"$(CDE_INSTALLATION_TOP)\" \
-		-I$(top_builddir)/include/Dt
+		$(DT_INCDIR)
 
 dtspcd_LDADD = $(DTCLIENTLIBS) $(XTOOLLIB)
 

cde/programs/dtterm/Makefile.am

@@ -11,7 +11,7 @@ endif
 dtterm_CFLAGS = -I$(top_builddir)/lib/DtTerm/TermPrim	\
 	-I$(top_builddir)/lib/DtTerm/Term			\
 	-I$(top_builddir)/lib/DtTerm/TermView $(TIRPCINC)	\
-	-I$(top_builddir)/include/Dt \
+	$(DT_INCDIR) \
 	-DSUN_TERMINAL_SERVER
 
 dtterm_SOURCES = DtTermLogit.c DtTermMain.c DtTermFallBackResources.c	\