with git bisect, like repeating

 24  2015-02-21 10:36  git bisect good
 25  2015-02-21 10:37  git g |head
 26  2015-02-21 10:37  sudo rm -rf /export/WRKOBJDIR/obj/sys
 27  2015-02-21 10:37  time sudo ./build.sh 
    -j 24 -m i386 
    -O /export/WRKOBJDIR/obj 
    -T /export/WRKOBJDIR/obj/tooldir.NetBSD-7.99.4-amd6 
    kernel=GENERIC >& /export/GENERIC.8b89467
 28  2015-02-21 10:38  scp 
    /export/WRKOBJDIR/obj/sys/arch/i386/compile/GENERIC/netbsd 
    192.168.1.38:/tmp/netbsd-2014-10-18-d24e104
 29  2015-02-21 10:38  ssh 192.168.1.38
 30  2015-02-21 10:41  git bisect bad

Following commit was the problem

commit 5aa0cfc14e3a920685630ca7740d2fe976544edd
Author: uebayasi <uebayasi@netbsd.org>
Date:   Fri Oct 17 20:55:21 2014 +0000

    Fix another indirect circular dependency (agp_* -> (agpbus) -> pchb -> abp_*).
    Fixes "no agp*" build.  Reported & build-tested by Kurt Schreiner.

diff --git a/sys/arch/x86/pci/files.pci b/sys/arch/x86/pci/files.pci
index f5d019a..c015803 100644
--- a/sys/arch/x86/pci/files.pci
+++ b/sys/arch/x86/pci/files.pci
@@ -1,4 +1,4 @@
-#	$NetBSD: files.pci,v 1.16 2014/06/10 01:42:39 hikaru Exp $
+#	$NetBSD: files.pci,v 1.17 2014/10/17 20:55:21 uebayasi Exp $
 
 device 	aapic
 attach 	aapic at pci
@@ -9,9 +9,7 @@ file	arch/x86/pci/agp_machdep.c	agp
 define amdnb_miscbus {}
 
 # PCI-Host bridge chipsets
-device	pchb:	pcibus, agpbus,
-		agp_ali, agp_amd, agp_amd64, agp_i810,
-		agp_intel, agp_sis, agp_via
+device	pchb:	pcibus, agpbus
 attach	pchb at pci
 file	arch/x86/pci/pchb.c		pchb		needs-flag
 

h87@makoto 11:30:08/150221(/export/netbsd-src)% git bisect bad c2dc1a9
Bisecting: 439 revisions left to test after this (roughly 9 steps)
error: Your local changes to the following files would be overwritten by checkout:
        sys/arch/x86/pci/files.pci
Please, commit your changes or stash them before you can switch branches.
Aborting
h87@makoto 11:30:14/150221(/export/netbsd-src)% git commit -m 'local change for agp' .
[detached HEAD 3508074] local change for agp
 1 file changed, 3 insertions(+), 1 deletion(-)
h87@makoto 11:30:44/150221(/export/netbsd-src)% git bisect bad c2dc1a9                
Bisecting: 439 revisions left to test after this (roughly 9 steps)
[521374a9f74235bd76511cfdc61b99dae29ee588] Ensure -- filemon is at start of line

sys/external/bsd/drm2/dist/drm/i915/i915_drv.h:
   #define INTEL_INFO(dev)  (&to_i915(dev)->info)

あるいは