libnfnetlink: quote $(FPIC) on command line

When $(FPIC) gets expanded on the command line (for instance
when setting environment variables for libtool, configure, or
make) we can't count on it not needing quoting (i.e. it could
contain multiple flags separated with spaces).

Fixes: dc31191ec3 ("build: make sure asm gets built with -DPIC")
Signed-off-by: Philip Prindeville <philipp@redfish-solutions.com>
(cherry picked from commit 7fae64cc06)

package/libs/libnfnetlink/Makefile

@@ -9,7 +9,7 @@ include $(TOPDIR)/rules.mk
 
 PKG_NAME:=libnfnetlink
 PKG_VERSION:=1.0.1
-PKG_RELEASE:=3
+PKG_RELEASE:=4
 
 PKG_SOURCE:=$(PKG_NAME)-$(PKG_VERSION).tar.bz2
 PKG_SOURCE_URL:= \
@@ -45,7 +45,7 @@ CONFIGURE_ARGS += \
 	--enable-shared
 
 CONFIGURE_VARS += \
-	lt_prog_compiler_pic=$(FPIC)
+	lt_prog_compiler_pic="$(FPIC)"
 
 define Build/InstallDev
 	$(INSTALL_DIR) $(1)/usr/include/libnfnetlink