libftdi1: fix pkgconfig file

Signed-off-by: Nicolas Thill <nico@openwrt.org>

libs/libftdi1/Makefile

@@ -67,6 +67,12 @@ define Build/InstallDev
 	$(CP) $(PKG_INSTALL_DIR)/usr/lib/cmake/libftdi1/* $(1)/usr/lib/cmake/libftdi1/
 	$(INSTALL_DIR) $(1)/usr/lib/pkgconfig/
 	$(CP) $(PKG_INSTALL_DIR)/usr/lib/pkgconfig/libftdi1.pc $(1)/usr/lib/pkgconfig/libftdi1.pc
+	$(SED) \
+		's,/usr/include,$$$${prefix}/include,g' \
+		 $(1)/usr/lib/pkgconfig/libftdi1.pc
+	$(SED) \
+		's,/usr/lib,$$$${prefix}/lib,g' \
+		 $(1)/usr/lib/pkgconfig/libftdi1.pc
 endef
 
 define Package/libftdi1/install