makefiles: Add makefile variables for the winegcc parameters.

Make.vars.in

@@ -18,6 +18,8 @@ SHELL           = /bin/sh
 RM              = rm -f
 MV              = mv
 CC              = @CC@
+CXX             = @CXX@
+CPPBIN          = @CPPBIN@
 CROSSCC         = @CROSSCC@
 CFLAGS          = @CFLAGS@
 CPPFLAGS        = @CPPFLAGS@

tools/winegcc/Makefile.in

@@ -14,8 +14,8 @@ winegcc_EXTRADEFS = \
 	-DDLLDIR="\"${dlldir}\"" \
 	-DLIBDIR="\"${libdir}\"" \
 	-DCC="\"$(CC)\"" \
-	-DCPP="\"@CPPBIN@\"" \
-	-DCXX="\"@CXX@\"" \
+	-DCPP="\"$(CPPBIN)\"" \
+	-DCXX="\"$(CXX)\"" \
 	-DPRELINK="\"$(PRELINK)\""
 
 winegcc$(EXEEXT): winegcc.o utils.o