ctest: Pass CTEST_SITE/CTEST_BUILD_NAME to configure step When performing the configure step in dashboard client mode, propagate `CTEST_SITE` and `CTEST_BUILD_NAME` as the `SITE` and `BUILDNAME` respective cache variables. This causes the values recorded in `DartConfiguration.tcl` to match those specified by the user, allowing subsequent ctest calls to reuse them automatically.