nss: create checksum files for the nss libraries

nss: create checksum files for the nss libraries

Add checksum files required for the NSS softoken to operate in FIPS 140 mode.
The shlibsign is invoked to sign the libraries, and it is built for the target
architecture and doesn't support cross-compiling so far.

Invoke shlibsign at target's first boot time to generate checksum files.

https://developer.mozilla.org/en-US/docs/NSS/NSS_Tech_Notes/nss_tech_note6
http://en.wikipedia.org/wiki/FIPS_140
https://bugzilla.mozilla.org/show_bug.cgi?id=681624

(From OE-Core rev: a4580f967c8064294a06d406acf5deb24aee2acc)

Signed-off-by: Hongxu Jia <hongxu.jia@windriver.com>
Signed-off-by: Saul Wold <sgw@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>