Several minor questions (12.0-amd64)

Hello, I have several brief questions on issues I'm slightly stuck on:

1. For buildworld, my /etc/src.conf uses default CROSS_COMPILER,
CLANG_BOOTSTRAP, CLANG_FULL  for amd64, but I would like clang to xbuild
only for target i386 as I do not need the others (like Target/arm). Is
there a knob for this?

2. Is there a way to read a list of modules inside an unloaded kernel? Sort
of "kldstat -v" for a non-loaded kernel? Reading the kernel manifest
(INCLUDE_CONFIG_FILE setting) is not what I need.

3. Under one scenario, I'm getting a kernel panic but I cannot dump because
busybox states "no dumpdev specified" which means rc.conf (where I have
dumpdev set) has not been read yet. How can I pass dumpdev wile in busybox
command line so that ">dump" does its job?

4. Getting several of these lock order reversals. Kernel is drm-next but
Generic from Head gives the same messages. Not urgent, just FYI.

lock order reversal:
 1st 0xfffff80064915040 filedesc structure (filedesc structure) _at_
/asp/git/srcdrm/sys/kern/kern_descrip.c:1234
 2nd 0xfffff8002e9f0d50 ufs (ufs) _at_
/asp/git/srcdrm/sys/kern/vfs_subr.c:5022
 stack backtrace:
 #0 0xffffffff804d3180 at witness_debugger+0x70
 #1 0xffffffff804d3073 at witness_checkorder+0xe23
 #2 0xffffffff8044aa35 at __lockmgr_args+0x875
 #3 0xffffffff814d09e5 at ffs_lock+0xa5
 #4 0xffffffff80717840 at VOP_LOCK1_APV+0xe0
 #5 0xffffffff8054847a at _vn_lock+0x6a
 #6 0xffffffff8042c9c8 at knlist_remove_kq+0x88
 #7 0xffffffff8053f358 at filt_vfsdetach+0x28
 #8 0xffffffff8042d4f1 at knote_fdclose+0x171
 #9 0xffffffff804206b5 at closefp+0x65
 #10 0xffffffff806afe9a at amd64_syscall+0x57a
 #11 0xffffffff80692dcb at Xfast_syscall+0xfb

 lock order reversal:
 1st 0xfffff80064915040 filedesc structure (filedesc structure) _at_
/asp/git/srcdrm/sys/kern/kern_descrip.c:1234
 2nd 0xfffff8004b4d3d50 zfs (zfs) _at_
/asp/git/srcdrm/sys/kern/vfs_subr.c:5022
 stack backtrace:
 #0 0xffffffff804d3180 at witness_debugger+0x70
 #1 0xffffffff804d3073 at witness_checkorder+0xe23
 #2 0xffffffff8044a0fe at lockmgr_lock_fast_path+0x1ce
 #3 0xffffffff80717840 at VOP_LOCK1_APV+0xe0
 #4 0xffffffff8054847a at _vn_lock+0x6a
 #5 0xffffffff8042c9c8 at knlist_remove_kq+0x88
 #6 0xffffffff8053f358 at filt_vfsdetach+0x28
 #7 0xffffffff8042d4f1 at knote_fdclose+0x171
 #8 0xffffffff804206b5 at closefp+0x65
 #9 0xffffffff806afe9a at amd64_syscall+0x57a
 #10 0xffffffff80692dcb at Xfast_syscall+0xfb

 lock order reversal:
 1st 0xfffff801aec715f0 syncer (syncer) _at_
/asp/git/srcdrm/sys/kern/vfs_subr.c:2152
 2nd 0xfffff8004bc3e068 zfs (zfs) _at_
/asp/git/srcdrm/sys/kern/vfs_subr.c:2602
 stack backtrace:
 #0 0xffffffff804d3180 at witness_debugger+0x70
 #1 0xffffffff804d3073 at witness_checkorder+0xe23
 #2 0xffffffff8044a0fe at lockmgr_lock_fast_path+0x1ce
 #3 0xffffffff80717840 at VOP_LOCK1_APV+0xe0
 #4 0xffffffff8054847a at _vn_lock+0x6a
 #5 0xffffffff80538892 at vget+0x82
 #6 0xffffffff8053a936 at vfs_msync+0xa6
 #7 0xffffffff8053ef96 at sync_fsync+0xc6
 #8 0xffffffff80716890 at VOP_FSYNC_APV+0xe0
 #9 0xffffffff8053d2fc at sched_sync+0x36c
 #10 0xffffffff80436f44 at fork_exit+0x84
 #11 0xffffffff8069301e at fork_trampoline+0xe

 lock order reversal:
 1st 0xfffff80039590d50 zfs (zfs) _at_
/asp/git/srcdrm/sys/kern/vfs_mount.c:855
 2nd 0xfffff8001a4489a0 devfs (devfs) _at_
/asp/git/srcdrm/sys/kern/vfs_subr.c:2602
 stack backtrace:
 #0 0xffffffff804d3180 at witness_debugger+0x70
 #1 0xffffffff804d3073 at witness_checkorder+0xe23
 #2 0xffffffff8044a0fe at lo
 ckmgr_lock_fast_path+0x1ce
 #3 0xffffffff80717840 at VOP_LOCK1_APV+0xe0
 #4 0xffffffff8054847a at _vn_lock+0x6a
 #5 0xffffffff80538892 at vget+0x82
 #6 0xffffffff80395b2d at devfs_allocv+0xcd
 #7 0xffffffff80395643 at devfs_root+0x43
 #8 0xffffffff8052f66f at vfs_donmount+0x118f
 #9 0xffffffff8052e4b2 at sys_nmount+0x72
 #10 0xffffffff806afe9a at amd64_syscall+0x57a
 #11 0xffffffff80692dcb at Xfast_syscall+0xfb