Remove empty generated file upon gperf failure

Prior to this change the build could fail as follows, if gperf is not
available (or fails):

  - make(1) stops due to the gperf error, but an empty target file
    (cfns.h) is still created
  - the empty cfns.h is newer than the source cfns.gperf so it is not
    regenerated on subsequent builds
  - the gcc build fails (undefined reference to libc_name_p)

Sponsored by:	The FreeBSD Foundation
MFC after:	3 days


git-svn-id: svn+ssh://svn.freebsd.org/base/head@275804 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f
Fix incorrect type of "invalids" argument in __iconv() prototype.


git-svn-id: svn+ssh://svn.freebsd.org/base/head@275805 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f