It is declared as
<hash>ifdef HAVE_ACPI
Bool xf86acpiDisableFlag = FALSE;
<hash>endif
in hw/xfree86/common/xf86Globals.c
but not protected by the ifdef in the sdk header xf86Priv.h, what
caused a build failure in the tinderbox, due to the address of the
symbol being taken (to ensure it is available) in sdksyms.c.
bf4c29ab48