fix: NONIUS_RUNNER generates main()

[chardan]

Despite this: `#define NONIUS_RUNNER

include <nonius.h++>`

...main() was not being generated by the examples.

Signed-off-by: Jesse Williamson jwilliamson@suse.de

[rmartinho]

From the guide:

The library itself is header-only so you don't have to build it. It comes as a single header that you can drop somewhere and #include it in your code. You can grab the header from the releases page.

The examples build just fine if you follow the instructions.

If you want to build the examples from the repo directly, you need to build them by running ninja examples.