Can't compile PG 17 (master) from git under Msys2 autoconf

I've been having trouble compiling PG 17 using msys2 / mingw64 (sorry my
meson setup is a bit broken at moment, so couldn't test that.).

Both my msys2 envs (Rev2, Built by MSYS2 project) 13.2.0 and my older
setup (x86_64-posix-seh-rev0, Built by MinGW-W64 project) 8.1.0

Have the same issue:

The error is

rm -f '../../src/include/storage/lwlocknames.h'
cp -pR ../../backend/storage/lmgr/lwlocknames.h
'../../src/include/storage/lwlocknames.h'
cp: cannot stat '../../backend/storage/lmgr/lwlocknames.h': No such file or
directory
make[1]: *** [Makefile:143: ../../src/include/storage/lwlocknames.h] Error 1
make[1]: Leaving directory '/projects/postgresql/postgresql-git/src/backend'
make: *** [../../src/Makefile.global:382: submake-generated-headers] Error 2

I traced the issue down to this change in
https://git.postgresql.org/gitweb/?p=postgresql.git;a=commit;h=721856ff24b

$(top_builddir)/src/include/storage/lwlocknames.h:
storage/lmgr/lwlocknames.h
- prereqdir=`cd '$(dir $<)' >/dev/null && pwd` && \
- cd '$(dir $@)' && rm -f $(notdir $@) && \
- $(LN_S) "$$prereqdir/$(notdir $<)" .
+ rm -f '$@'
+ $(LN_S) ../../backend/$< '$@'

$(top_builddir)/src/include/utils/wait_event_types.h:
utils/activity/wait_event_types.h
- prereqdir=`cd '$(dir $<)' >/dev/null && pwd` && \
- cd '$(dir $@)' && rm -f $(notdir $@) && \
- $(LN_S) "$$prereqdir/$(notdir $<)" .
+ rm -f '$@'
+ $(LN_S) ../../backend/$< '$@'

Reverting just the above change fixes the issue. I'm not sure what all that
does to be honest, so not sure the best way to move forward.
My linux autoconf build systems do not have this issue.

Thanks,
Regina