make clean deleting source files

[Tom Ritter]

I performed the following sequence of commands:

$ wget ftp://ftp.gnupg.org/gcrypt/gnupg/gnupg-2.0.15.tar.bz2
$ tar xfj gnupg-2.0.15.tar.bz2
$ cd gnupg-2.0.15
$ ./configure
$ stat common/status-codes.h
$ make
$ stat common/status-codes.h
$ make clean
$ stat common/status-codes.h     <- file is now missing

At that point, I am unable to run 'make'.  I'm not familiar with the
complex Makefile and Makefile-generating tools, but removing the source
file is intentional per line 30 in common\Makefile.am

> CLEANFILES = audit-events.h status-codes.h

Those lines have been present since 2007 (revision 4628).

I'm confused as to what's going on here - either something seems to be
wrong with 'make clean' (less likely given the age of the code) or I'm
misunderstanding what should happen when I run 'make clean'.

-tom