strange compile error in scvgarndr.c

I'm seeing this very strange error when I try to make a kernel using
sources updated about 5 minutes ago:

--------------------------------------------------------------
>>> stage 3.1: building everything
--------------------------------------------------------------
/usr/src/sys/dev/syscons/scvgarndr.c:177:31: error: unused variable 'mouse10x16'
      [-Werror,-Wunused-const-variable]
static const struct mousedata mouse10x16 = { {
                              ^
1 error generated.
*** Error code 1

Even if I add "mpd = &mouse10x16;" before the test for font size in
various places the compiler spits out this error message.

Maybe my compiler is too old? I'm using
cc --version
FreeBSD clang version 4.0.0 (branches/release_40 296509) (based on LLVM 4.0.0)
Target: x86_64-unknown-freebsd12.0
Thread model: posix
InstalledDir: /usr/bin

-- 
Gary Jennejohn