Use host compiler to build 'gen' since it's run when building.

Signed-off-by: Gustavo Zacarias <gustavo@zacarias.com.ar>

diff -Nura bind-9.5.1-P1/lib/dns/Makefile.in bind-9.5.1-P1.gencross/lib/dns/Makefile.in
--- bind-9.5.1-P1/lib/dns/Makefile.in	2007-09-11 22:09:08.000000000 -0300
+++ bind-9.5.1-P1.gencross/lib/dns/Makefile.in	2009-03-04 16:35:23.000000000 -0200
@@ -160,8 +160,8 @@
 	./gen -s ${srcdir} > code.h

 gen: gen.c
-	${BUILD_CC} ${BUILD_CFLAGS} -I${top_srcdir}/lib/isc/include \
-	${BUILD_CPPFLAGS} ${BUILD_LDFLAGS} -o $@ ${srcdir}/gen.c ${BUILD_LIBS}
+	${HOSTCC} ${HOST_CFLAGS} -I${top_srcdir}/lib/isc/include \
+	${HOST_LDFLAGS} -o $@ ${srcdir}/gen.c

 rbtdb64.@O@: rbtdb.c