include_gardener fails to build in a corporate environment because the cmake build tries to download googletest directly from the internet

[marlowa]

The build was on a RHEL8 machine using gcc 8.5. The machine is in a corporate environment where direct internet access is not allowed.

Here is the error report:

[1/9] Creating directories for 'googletest'
[2/9] Performing download step (git clone) for 'googletest'
FAILED: googletest-prefix/src/googletest-stamp/googletest-download /home/marlowa/work/include_gardener-1.0.0/build/googletest-download/googletest-prefix/src/googletest-stamp/googletest-download
cd /home/marlowa/work/include_gardener-1.0.0/build && /usr/bin/cmake -P /home/marlowa/work/include_gardener-1.0.0/build/googletest-download/googletest-prefix/tmp/googletest-gitclone.cmake && /usr/bin/cmake -E touch /home/marlowa/work/include_gardener-1.0.0/build/googletest-download/googletest-prefix/src/googletest-stamp/googletest-download
Cloning into 'googletest-src'...
fatal: unable to access 'https://github.com/google/googletest.git/': Could not resolve host: github.com
Cloning into 'googletest-src'...
fatal: unable to access 'https://github.com/google/googletest.git/': Could not resolve host: github.com
Cloning into 'googletest-src'...
fatal: unable to access 'https://github.com/google/googletest.git/': Could not resolve host: github.com
-- Had to git clone more than once: 3 times.
CMake Error at googletest-download/googletest-prefix/tmp/googletest-gitclone.cmake:39 (message):
Failed to clone repository: 'https://github.com/google/googletest.git'

Please provide a documented way to omit that aspect of the build.