WIP: Support for lcov/gcov with Ninja

[giacomini]

This is an attempt to better integrate the Ninja build system (issue #29, but also #6).

It is just meant for discussion, for there are still a few things to sort out, e.g. the target versions of CMake, Ninja, gcc, ... It's a bit of a mess.

Whatever the response, it would be nice to have a github action that runs tests for at least some combinations of the above.

[codecov-commenter]

Codecov Report

Merging #30 (115a51d) into master (06a61fc) will not change coverage. The diff coverage is n/a.

@@            Coverage Diff            @@
##            master       #30   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            5         4    -1     
  Lines           20        17    -3     
=========================================
- Hits            20        17    -3     

Impacted Files	Coverage Δ
src/fortran/hello.f

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