CTest: Add support for Intel coverage files

By default, Intel compiler coverage tools
generate HTML files as reports, but the option
-txtlcov can be given to codecov to output
a coverage file with LCov format.

To use Intel coverage:

build the project with coverage flags
run the application
run profmerge
run codecov

The output file will be generated as build_dir
/CodeCoverage/SRCFILEDIR.LCOV