tools.mk: Expose tiny_ssim.SRCS as tiny_ssim_srcs.txt

This CL adds the change to get the source files to build the tiny_ssim
binary.

Bug: 410594665
Change-Id: I3679b22c6b68130e5f874fbecb188fa2f28eed67
(cherry picked from commit 748eb8338906a21e1a68d6aaf1c17af345140e1b)

Change-Id: I3679b22c6b68130e5f874fbecb188fa2f28eed67
2 files changed