contrib: Fix x265.pc on osx

Works around cmake

(cherry picked from commit 2703bbacb86dd79ecad9520093a1b1e3e2b423d5)
Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>

contrib/src/x265/rules.mak

@@ -32,4 +32,5 @@ x265: x265-$(X265_VERSION).tar.bz2 .sum-x265
 .x265: x265 toolchain.cmake
 	cd $</source && $(HOSTVARS_PIC) $(CMAKE) -DENABLE_SHARED=OFF
 	cd $</source && $(MAKE) install
+	sed -e s/'[^ ]*clang_rt[^ ]*'//g -i.orig "$(PREFIX)/lib/pkgconfig/x265.pc"
 	touch $@