zmq: fix pkgconfig file

It seems upstream broke it. This in turn broke depending packages.

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

libs/zmq/Makefile

@@ -11,7 +11,7 @@ include $(TOPDIR)/rules.mk
 
 PKG_NAME:=zeromq
 PKG_VERSION:=4.3.2
-PKG_RELEASE:=1
+PKG_RELEASE:=2
 
 PKG_SOURCE:=$(PKG_NAME)-$(PKG_VERSION).tar.gz
 PKG_SOURCE_URL:=https://github.com/zeromq/libzmq/releases/download/v$(PKG_VERSION)
@@ -91,6 +91,8 @@ define Build/InstallDev
 	$(CP) $(PKG_INSTALL_DIR)/usr/lib/libzmq.so* $(1)/usr/lib/
 	$(INSTALL_DIR) $(1)/usr/lib/pkgconfig
 	$(CP) $(PKG_INSTALL_DIR)/usr/lib/pkgconfig/libzmq.pc $(1)/usr/lib/pkgconfig/
+	$(SED) 's,/usr/include,$$$${prefix}/include,g' $(1)/usr/lib/pkgconfig/libzmq.pc
+	$(SED) 's,/usr/lib,$$$${exec_prefix}/lib,g' $(1)/usr/lib/pkgconfig/libzmq.pc
 endef
 
 define Package/libzmq-nc/install