Clang on FreeBSD was complaining:
```csh
[ 26%] Building C object CMakeFiles/criterion.dir/src/core/abort.c.o
[ 30%] Building C object CMakeFiles/criterion.dir/src/core/report.c.o
[ 30%] Building C object CMakeFiles/criterion.dir/src/core/runner.c.o
In file included from /root/projects/Criterion/Criterion/Criterion/src/core/runner.c:29:
/root/projects/Criterion/Criterion/Criterion/dependencies/valgrind/include/valgrind/valgrind.h:6223:29: error: unused
parameter 'format' [-Werror,-Wunused-parameter]
VALGRIND_PRINTF(const char *format, ...)
^
/root/projects/Criterion/Criterion/Criterion/dependencies/valgrind/include/valgrind/valgrind.h:6261:39: error: unused
parameter 'format' [-Werror,-Wunused-parameter]
VALGRIND_PRINTF_BACKTRACE(const char *format, ...)
^
2 errors generated.
```
The other way to fix it was to add a compiler option in CMake:
```cmake
add_compile_options(-Wno-unused-parameter)
```
but this approach disables the check globally.
I am not sure whether there is a way to scope
the compiler option to a subdirectory; especially
in cases where submodule (via `add_subdirectory`)
headers have unsed parameters.
