Fix to let relative include helper ignore non-C files

[lhstrh]

Fixes #1576.

[arengarajan99]

Looks like the problem is stemming from multiple definitions of the main function (one gets done automatically by Arduino to call setup and loop and the other is coming from a test file for the hashset implementation.) Ideally, the test file should not be copied over and it should resolve.

@edwardalee Are you able to move that test file into https://github.com/lf-lang/reactor-c/tree/main/test/general/utils ? It would be the easiest fix as far as Peter and I know.

[lhstrh]

Makes sense to have tests either have the word "test" in them or group them in a directory called "test." That way, we can easily ignore them.

[lhstrh]

Looks like the problem is stemming from multiple definitions of the main function (one gets done automatically by Arduino to call setup and loop and the other is coming from a test file for the hashset implementation.) Ideally, the test file should not be copied over and it should resolve.

@edwardalee Are you able to move that test file into https://github.com/lf-lang/reactor-c/tree/main/test/general/utils ? It would be the easiest fix as far as Peter and I know.

I went ahead and moved the file. It now also gets run as part of the unit tests.