Compiler wasn't happy about strncpy() depending on the source's length and not
the target's, but this whole thing can be simplified by simply using asprintf()
(which is already used in this file, so no #include necessary).

run.c: In function ‘main._omp_fn.0’:
run.c:964:21: warning: ‘strncpy’ specified bound depends on the length of the source argument [-Wstringop-overflow=]
                     strncpy(out_filename, current_shader_name,
                     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
                             strlen(current_shader_name) + 1);
                             ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Signed-off-by: Eric Engestrom <eric.engestrom@intel.com>
Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>