qemu: fix build failure caused by ld cannot find iconv

This was caused by upstream project commit db5adeaa ("build-sys: clean
up flags included in the linker command line")

Reported-by: W. Michael Petullo <mike@flyn.org>
Link: https://github.com/openwrt/packages/issues/13081
Signed-off-by: Yousong Zhou <yszhou4tech@gmail.com>

utils/qemu/Makefile

@@ -10,7 +10,7 @@ include $(TOPDIR)/rules.mk
 
 PKG_NAME:=qemu
 PKG_VERSION:=5.0.0
-PKG_RELEASE:=2
+PKG_RELEASE:=3
 PKG_SOURCE:=$(PKG_NAME)-$(PKG_VERSION).tar.xz
 PKG_HASH:=2f13a92a0fa5c8b69ff0796b59b86b080bbb92ebad5d301a7724dd06b5e78cb6
 PKG_SOURCE_URL:=http://download.qemu.org/
@@ -288,9 +288,9 @@ CONFIGURE_ARGS +=			\
 	--host-cc="$(HOSTCC)"		\
 	--disable-fortify-source	\
 	--disable-stack-protector	\
-	--extra-cflags="$(EXTRA_CFLAGS)"	\
-	--extra-cxxflags="$(EXTRA_CXXFLAGS)"	\
-	--extra-ldflags="$(EXTRA_LDFLAGS)"	\
+	--extra-cflags="$(TARGET_CFLAGS) $(EXTRA_CFLAGS)"	\
+	--extra-cxxflags="$(TARGET_CXXFLAGS) $(EXTRA_CXXFLAGS)"	\
+	--extra-ldflags="$(TARGET_LDFLAGS) $(EXTRA_LDFLAGS)"	\
 
 # VHost features
 CONFIGURE_ARGS +=			\