protobuf-c: Disable protoc for host build

On some platforms, the host build is failing as the tests fail. protoc is
not used anyway.

Signed-off-by: Rosen Penev <rosenp@gmail.com>

libs/protobuf-c/Makefile

@@ -9,7 +9,7 @@ include $(TOPDIR)/rules.mk
 
 PKG_NAME:=libprotobuf-c
 PKG_VERSION:=1.3.1
-PKG_RELEASE:=1
+PKG_RELEASE:=2
 
 PKG_SOURCE:=protobuf-c-$(PKG_VERSION).tar.gz
 PKG_SOURCE_URL:=https://github.com/protobuf-c/protobuf-c/releases/download/v$(PKG_VERSION)
@@ -43,6 +43,9 @@ define Package/libprotobuf-c/description
   internal RPC protocols and file formats.
 endef
 
+HOST_CONFIGURE_ARGS += \
+	--disable-protoc
+
 CONFIGURE_ARGS += \
 	--enable-shared \
 	--enable-static \