I get the following when trying to build rc5-mm1:

arch/i386/kernel/setup.c:99: error: parse error before "acpi_sci_flags"
arch/i386/kernel/setup.c:99: warning: type defaults to `int' in declaration
of `acpi_sci_flags'
arch/i386/kernel/setup.c:99: warning: data definition has no type or
storage class
arch/i386/kernel/setup.c: In function `parse_cmdline_early':
arch/i386/kernel/setup.c:836: error: request for member `trigger' in
something not a structure or union
arch/i386/kernel/setup.c:839: error: request for member `trigger' in
something not a structure or union
arch/i386/kernel/setup.c:842: error: request for member `polarity' in
something not a structure or union
arch/i386/kernel/setup.c:845: error: request for member `polarity' in
something not a structure or union
make[1]: *** [arch/i386/kernel/setup.o] Error 1
make[1]: *** Waiting for unfinished jobs....

Looks like when #ifdef CONFIG_ACPI was added to include/linux/acpi.h it
broke things b/c acpi_sci_flags is needed for CONFIG_ACPI_BOOT, which
depends on X86_HT || ACPI.  Thus, you can have ACPI=n, and X86_HT=y &
ACPI_BOOT=y and it won't build.  This patch at least gets it to build for me...

-Matt