HPCC-10526 add testing/regress to platform and clienttools install
Add <INSTALL_HOME>/testing/regress, exclude ecl directory which has internal testcases
ADD <INSTALL_HOME>/testing/regress to PATH environment variable for platform
Create symbolic link for ecl-test in clienttools install and remove it when uninstalling.
Merge pull request #5407 from xwang2713/HPCC-10526

HPCC-10526 add regress to Platform and Clienttools distribution packages

Reviewed-By: Richard Chapman <rchapman@hpccsystems.com>