contrib: Flac needs USE_OBSOLETE_SIGCONTEXT_FLAVOR on Android-x86

Headers normally present under normal Linux are missing in bionic.
Signed-off-by: Rafaël Carré <funman@videolan.org>

contrib/src/flac/rules.mak

@@ -19,6 +19,13 @@ flac: flac-$(FLAC_VERSION).tar.gz .sum-flac
 	$(APPLY) $(SRC)/flac/libFLAC-pc.patch
 ifdef HAVE_DARWIN_OS
 	cd $(UNPACK_DIR) && sed -e 's,-dynamiclib,-dynamiclib -arch $(ARCH),' -i.orig configure
+endif
+ifdef HAVE_ANDROID
+ifeq ($(ANDROID_ABI), x86)
+	# cpu.c:130:29: error: sys/ucontext.h: No such file or directory
+	# defining USE_OBSOLETE_SIGCONTEXT_FLAVOR allows us to bypass that
+	cd $(UNPACK_DIR) && sed -i.orig -e s/"#  undef USE_OBSOLETE_SIGCONTEXT_FLAVOR"/"#define USE_OBSOLETE_SIGCONTEXT_FLAVOR"/g src/libFLAC/cpu.c
+endif
 endif
 	$(UPDATE_AUTOCONFIG)
 	$(MOVE)