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>
diff --git a/BUILD.gn b/BUILD.gn
index 4080562..3b6db2d 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -3108,3 +3108,9 @@
     deps = [ "tools/skottie_ios_app" ]
   }
 }
+
+executable("skia_c_api_example") {
+  sources = [ "experimental/c-api-example/skia-c-example.c" ]
+  include_dirs = [ "." ]
+  deps = [ ":skia" ]
+}