jtg: fix compile on platforms with VFP

buildbot reported error on platforms with VFP (sunxi,imx6,omap):
ld: error: jtg uses VFP register arguments, /tmp/ccewx1gu.o does not

CFLAGS were overwritten so append them instead

Signed-off-by: Dirk Neukirchen <dirkneukirchen@web.de>
Signed-off-by: Florian Fainelli <florian@openwrt.org>

git-svn-id: svn://svn.openwrt.org/openwrt/packages@40788 3c298f89-4303-0410-b956-a3cf2f4a3e73

net/jtg/patches/001-Makefile_honor_CFLAGS_for_VFP.patch

@@ -0,0 +1,11 @@
+--- a/Makefile
++++ b/Makefile
+@@ -2,7 +2,7 @@ BINDIR= $(HOME)/bin
+ VERSION=1.95
+ 
+ CC = gcc
+-CFLAGS= -O3 -Wall -Winline -pedantic
++CFLAGS+= -O3 -Wall -Winline -pedantic
+ CFLAGS+= -g
+ 
+ # The "-DLinuxTCP" controls which TCP options are in use