[CMake] Automatically update `list.h`

[CMake] Automatically update `list.h`

`list.h` contains a list of all the tests and is generated
by grepping the test source files for `DEFINE_TEST`.
Previously, it was generated at configure time.
This meant that if you added a new test to an existing
source file, you had to manually reconfigure.

This adds the necessary dependencies so that `list.h`
is regenerated whenever any C test source changes.
This ensures that new tests are always discovered automatically.

Note:  If someone wants to update the autoconf-based
build system to do this, please send a PR.