https://bugs.gentoo.org/901099 and partly https://bugs.gentoo.org/900937.

Newer compilers may optimise such that < 7 registers are free on 32-bit x86
and then we get an "invalid asm" error. This is https://bugs.gentoo.org/901099
and https://trac.ffmpeg.org/ticket/8903.

Making matters worse, GCC sometimes hangs on invalid asm, so this also
mitigates a hang with e.g. -O3 -march=znver1. See https://bugs.gentoo.org/900937
and https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109137.

In future, we may want to adjust the definition of HAVE_7REGS to just exclude
32-bit x86, but that's a big sledgehammer, so let's avoid it for now until we have
a reply on the upstream ffmpeg bug.
--- a/libavcodec/x86/cabac.h
+++ b/libavcodec/x86/cabac.h
@@ -175,7 +175,7 @@

 #endif /* BROKEN_RELOCATIONS */

-#if HAVE_7REGS && !BROKEN_COMPILER
+#if HAVE_7REGS && !BROKEN_COMPILER && !ARCH_X86_32
 #define get_cabac_inline get_cabac_inline_x86
 static
 #if defined(_WIN32) && !defined(_WIN64) && defined(__clang__)