netpipe: fix compile on platforms with VFP

buildbot reported error on platforms with VFP (sunxi,imx6,omap):
 NPtcp uses VFP register arguments, /tmp/.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@40790 3c298f89-4303-0410-b956-a3cf2f4a3e73

net/netpipe/patches/001-Makefile_honor_CFLAGS_for_VFP.patch

@@ -0,0 +1,11 @@
+--- a/makefile
++++ b/makefile
+@@ -21,7 +21,7 @@
+ ########################################################################
+ 
+ CC         = cc
+-CFLAGS     = -O -g
++CFLAGS     += -O -g
+ SRC        = ./src
+ 
+ # For MPI, mpicc will set up the proper include and library paths