When loading the list of target support directories, read the file
with UTF-8 encoding since that is what CMake writes into the file.
This allows us to support international characters in the path to
the build tree containing the target support directories.
Add a GCOV_OPTIONS option to allow specification of custom flags. In
ctest_coverage gcov support, if you set CTEST_COVERAGE_EXTRA_FLAGS, they
get put on the command line before the -o. In this case we remove the
-b and replace it with GCOV_OPTIONS. All other arguments remain the
same.
Provide a function to run gcov and create a tarball of results.
Since CDash tracks the md5sum of the files uploaded, use the
--mtime option with "cmake -E tar" so that tar files could be
created that would have the same md5sum with the same content.