Increase cmake minimum version from 3.0 to 3.13. (#94)
Increase cmake minimum version from 3.0 to 3.13. (#94)

It was already at 3.13 for RUN_TEST=on. Now it's so for RUN_TEST=off, too,
based on anecdotal evidence. It's possible the actual minimum is somewhere in
between.
google/libsxg,google/libsxg,google/libsxg