[CMake] cmake policy setting

[Marco Atzeri]

As there is no example in the documentaion, 
could someone clarify me if the change of any policy
that should require an additional

cmake_policy(SET CMP<NNNN> NEW)


could also be requested at cmake invocation with  
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# -D <var>:<type>=<value>: Create a cmake cache entry.

When cmake is first run in an empty build tree, it creates a CMakeCache.txt file and populates it with customizable settings for the project. This option may be used to specify a setting that takes priority over the project's default value. The option may be repeated for as many cache entries as desired. 
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Regards
Marco