libpam: inherit pkgconfig

libpam: inherit pkgconfig

* missing dependency on pkgconfig-native was causing
  that PKG_CHECK_MODULES(DBUS, dbus-1) stayed unexpanded in
  configure script:
  checking for dbm_store in -lndbm... no
  libpam/1.1.6-r2/Linux-PAM-1.1.6/configure:
  line 14217: syntax error near unexpected token `libtirpc,'
  libpam/1.1.6-r2/Linux-PAM-1.1.6/configure:
  line 14217: `      PKG_CHECK_MODULES(libtirpc, libtirpc,'
  Configure failed. The contents of all config.log files follows to aid
  debugging

(From OE-Core rev: d8d230a164b4e98dbb3a9e6d9bb567c2aabee7f9)

Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>
Signed-off-by: Saul Wold <sgw@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>