libFLAC: Fix cpuid detecton on old Cyrix CPUs

Some old CPUs (eg Cyrix) set EDX but not ECX when executing CPUID.
One of the solutions is to clear ECX before calling cpuid. From
https://bugzilla.mozilla.org/show_bug.cgi?id=1096651#c9 bug

Patch-from: lvqcl <lvqcl.mail@gmail.com>

src/libFLAC/ia32/cpu_asm.nasm

@@ -78,6 +78,7 @@ cident FLAC__cpu_info_asm_ia32
 	cpuid
 	cmp	eax, 1
 	jb	.no_cpuid
+	xor	ecx, ecx
 	mov	eax, 1
 	cpuid
 	mov	ebx, [esp + 8]