...on alpha so far

I've just updated a box to -current, and now I can't
compile empty files anymore:

zel637: {21} ls -l mist.c
-rw-r--r--  1 drochner  ca1  0 Jan 13 19:31 mist.c
zel637: {22} cc -c mist.c
mist.o: File truncated
/var/tmp//ccYLeZtB.s: Assembler messages:
/var/tmp//ccYLeZtB.s:3: FATAL: Can't write mist.o: File truncated

This breaks kernel builds because some source files are effectively
empty if certain options are not set. (eg tcp_debug.c, ip_htable.c).

What might have caused this?

best regards
Matthias