The native DejaGnu unit testing support is provided by a library
module dejagnu.exp and the procedure
called by testsuite code to run unit tests.
host_execute program arguments
host_execute procedure runs program, passing
arguments on the command line, and examines the output for test
result messages according to the DejaGnu unit testing protocol.
If successful, the return value is an empty string. Otherwise, an error message is returned.