build: disable non-PIC assembly when building for Android/x86

This disables MMX/MMXEXT code for ffmpeg/postproc, and all assembly for
mpg123 and libass, if building for Android on x86 (32-bit).

It has performance implications but it avoids all TEXTRELs in the output,
which makes it possible to use W^X hardening techniques. The code can
probably be ported to be PIC-compatible in the future so that these can be
re-enabled, but even Gentoo Linux has no better solutions for this at the
moment.
Signed-off-by: Diego Elio Pettenò <flameeyes@flameeyes.eu>
Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>

contrib/src/ass/rules.mak

@@ -10,6 +10,9 @@ endif
 ifdef HAVE_ANDROID
 WITH_FONTCONFIG = 0
 WITH_HARFBUZZ = 0
+ifeq ($(ANDROID_ABI), x86)
+WITH_ASS_ASM = 0
+endif
 else
 ifdef HAVE_TIZEN
 WITH_FONTCONFIG = 0
@@ -59,6 +62,10 @@ else
 ASS_CONF += --disable-harfbuzz
 endif
 
+ifeq ($(WITH_ASS_ASM), 0)
+ASS_CONF += --disable-asm
+endif
+
 ifdef WITH_OPTIMIZATION
 ASS_CFLAGS += -O3
 else

contrib/src/ffmpeg/rules.mak

@@ -138,6 +138,12 @@ FFMPEGCONF += --target-os=linux --enable-pic
 
 endif
 
+ifdef HAVE_ANDROID
+ifeq ($(ANDROID_ABI), x86)
+FFMPEGCONF +=  --disable-mmx --disable-mmxext
+endif
+endif
+
 # Windows
 ifdef HAVE_WIN32
 ifndef HAVE_MINGW_W64

contrib/src/mpg123/rules.mak

@@ -7,6 +7,14 @@ ifeq ($(call need_pkg,"mpg123"),)
 PKGS_FOUND += mpg123
 endif
 
+MPG123CONF = $(HOSTCONF)
+
+ifdef HAVE_ANDROID
+ifeq ($(ANDROID_ABI), x86)
+MPG123CONF += --with-cpu=generic_fpu
+endif
+endif
+
 $(TARBALLS)/mpg123-$(MPG123_VERSION).tar.bz2:
 	$(call download,$(MPG123_URL))
 
@@ -22,6 +30,6 @@ endif
 
 .mpg123: mpg123
 	$(RECONF)
-	cd $< && $(HOSTVARS) ./configure $(HOSTCONF)
+	cd $< && $(HOSTVARS) ./configure $(MPG123CONF)
 	cd $< && $(MAKE) install
 	touch $@

contrib/src/postproc/rules.mak

@@ -73,6 +73,12 @@ ifdef HAVE_LINUX
 POSTPROCCONF += --target-os=linux --enable-pic
 endif
 
+ifdef HAVE_ANDROID
+ifeq ($(ANDROID_ABI), x86)
+POSTPROCCONF +=  --disable-mmx --disable-mmxext
+endif
+endif
+
 # Windows
 ifdef HAVE_WIN32
 POSTPROCCONF += --target-os=mingw32