Fix issues related to using CDash behind a proxy server

[zackgalbreath]

[lockywolf]

This pull request allowed me to install cdash under http://my.server/cdash/, although I am afraid, it does not fix all the difficulties. In particular, the generated CTestConfig.cmake does not seem to have the correct suffix added.

## This file should be placed in the root directory of your project.
## Then modify the CMakeLists.txt file in the root directory of your
## project to incorporate the testing dashboard.
##
## # The following are required to submit to the CDash dashboard:
##   ENABLE_TESTING()
##   INCLUDE(CTest)

set(CTEST_PROJECT_NAME "MyProjectSuperbuild")
set(CTEST_NIGHTLY_START_TIME "01:00:00 UTC")

set(CTEST_DROP_METHOD "http")
set(CTEST_DROP_SITE "my.server")
set(CTEST_DROP_LOCATION "/submit.php?project=LibraSuperbuild")
set(CTEST_DROP_SITE_CDASH TRUE)

I think that CTEST_DROP_LOCATION should be "/cdash/submit.php?project=LibraSuperbuild"

[lockywolf]

One more place where website root address doesn't seem to be used correctly is http://server.name/cdash/index.php?project=MyProject&date=2022-08-16.

Clicking on the build name seems to be redirecting without taking the prefix into account.