LU-13092 lbuild: include lbuild-{fc,rhel,sles} to SIGNATURE

LU-13092 lbuild: include lbuild-{fc,rhel,sles} to SIGNATURE

We should include these files to calculate SIGNATURE, for example
bump kernel extra tags could happen there.

Lustre-change: https://review.whamcloud.com/37076
Lustre-commit: b39e1e6e3e4ea396ad842ec3695f45cfd5dfb79e

Test-Parameters: trivial
Change-Id: I2c62ad765d3c6a1b9e99affe3be95a404d6140c5
Signed-off-by: Wang Shilong <wshilong@ddn.com>
Reviewed-by: Gu Zheng <gzheng@ddn.com>
Reviewed-by: Emoly Liu <emoly@whamcloud.com>
Reviewed-by: Minh Diep <mdiep@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>
Reviewed-on: https://review.whamcloud.com/37312
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>