This is testing with $kex, not without $kex, so use $kex, not "-$kex".
In test-ref-configs.pl, use $conf rather than "$conf". This is purely
a matter of Perl coding style.
Set MBEDTLS_TEST_PLATFORM and MBEDTLS_TEST_CONFIGURATION to meaningful
values in all.sh. These environment variables are used when
writing an outcome file, which happens if MBEDTLS_TEST_OUTCOME_FILE is
also set.
When running one of the try-multiple-configuration scripts, set
MBEDTLS_TEST_CONFIGURATION to a value that uniquely describes the
configuration.
