11.1-RELEASE-p10 cannot compile freebsd stable/11 kernel?

[Mike Karels]

I attempted a kernel compile from stable/11, as a freebsd-update didn't
seem to update /usr/src/sys, and I'm running a custom kernel.  I get
compile errors like this:

    ../../../amd64/amd64/support.S:829:2: error: unknown directive
     .altmacro
     ^
    <instantiation>:1:13: error: invalid register name
    handle_ibrs_%(ll):
		^~
    <instantiation>:3:2: note: while in macro instantiation
     ibrs_seq_label %(ll)
     ^
    <instantiation>:2:2: note: while in macro instantiation
     .rept 32
     ^
    ../../../amd64/amd64/support.S:858:2: note: while in macro instantiation
     ibrs_seq 32
     ^
    <instantiation>:1:13: error: invalid register name
    handle_ibrs_%(ll):
		^~
    <instantiation>:8:2: note: while in macro instantiation
     ibrs_seq_label %(ll)
     ^
    <instantiation>:2:2: note: while in macro instantiation
     .rept 32
     ^
    ../../../amd64/amd64/support.S:858:2: note: while in macro instantiation
     ibrs_seq 32
     ^
    <instantiation>:1:13: error: invalid register name
    handle_ibrs_%(ll):
(and this continues)

I had just run freebsd-update:

    pughole# freebsd-version
    11.1-RELEASE-p10


    pughole# cc --version
    FreeBSD clang version 4.0.0 (tags/RELEASE_400/final 297347) (based on LLVM 4.0.0)
    Target: x86_64-unknown-freebsd11.1
    Thread model: posix
    InstalledDir: /usr/bin

I know that clang has been updated a lot; has the kernel source gotten
ahead of clang on stable/11?

		Mike