Fix C API example, ensure the C API example is built in CI

Change-Id: I25529ec79bd53dcd475a959503d15b1be7d39970
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/344616
Reviewed-by: Mike Klein <mtklein@google.com>
Commit-Queue: Mike Klein <mtklein@google.com>
3 files changed