seen with trunk 20231229 on aarch64-linux-gnu, last successful build from 20231214

[...]
libtool: compile:  /<<PKGBUILDDIR>>/build/./gcc/gccgo -B/<<PKGBUILDDIR>>/build/./gcc/ -B/usr/aarch64-linux-gnu/bin/ -B/usr/aarch64-linux-gnu/lib/ -isystem /usr/aarch64-linux-gnu/include -isystem /usr/aarch64-linux-gnu/sys-include -isystem /<<PKGBUILDDIR>>/build/sys-include -O2 -g -I . -c -fgo-pkgpath=internal/goarch ../../../src/libgo/go/internal/goarch/goarch.go zgoarch.go  -fPIC -o internal/.libs/goarch.o
zgoarch.go:7:3: error: redefinition of ''
    7 |   _BigEndian = false
      |   ^
zgoarch.go:6:3: note: previous definition of '' was here
    6 |   _ArchFamily = ARM64
      |   ^
zgoarch.go:8:3: error: redefinition of ''
    8 |   _DefaultPhysPageSize = 65536
      |   ^
zgoarch.go:6:3: note: previous definition of '' was here
    6 |   _ArchFamily = ARM64
      |   ^
zgoarch.go:9:3: error: redefinition of ''
    9 |   _Int64Align = 8
      |   ^
zgoarch.go:6:3: note: previous definition of '' was here
    6 |   _ArchFamily = ARM64
      |   ^
zgoarch.go:10:3: error: redefinition of ''
   10 |   _MinFrameSize = 8
      |   ^
zgoarch.go:6:3: note: previous definition of '' was here
    6 |   _ArchFamily = ARM64
      |   ^
zgoarch.go:11:3: error: redefinition of ''
   11 |   _PCQuantum = 4
      |   ^
zgoarch.go:6:3: note: previous definition of '' was here
    6 |   _ArchFamily = ARM64
      |   ^
zgoarch.go:12:3: error: redefinition of ''
   12 |   _StackAlign = 16
      |   ^
zgoarch.go:6:3: note: previous definition of '' was here
    6 |   _ArchFamily = ARM64
      |   ^
../../../src/libgo/go/internal/goarch/goarch.go:8:21: error: expected type
    8 | type ArchFamilyType int
      |                     ^
zgoarch.go:6:17: error: constant refers to itself
    6 |   _ArchFamily = ARM64
      |                 ^
make[6]: *** [Makefile:3059: internal/goarch.lo] Error 1
make[6]: Leaving directory '/<<PKGBUILDDIR>>/build/aarch64-linux-gnu/libgo'
make[5]: *** [Makefile:2358: all-recursive] Error 1

complete build log at
https://launchpad.net/~doko/+archive/ubuntu/toolchain/+build/27596519/+files/buildlog_ubuntu-noble-arm64.gcc-14_14-20231229-0ubuntu1_BUILDING.txt.gz