FindBoost: Remove obsolete diagnostic message about Boost_ROOT
CMake 3.12
introduced <package>_ROOT
CMake and environment variables to
be valid hints to find_package(<package>)
. Defining Boost_ROOT
is no
longer wrong if CMP0074
is set to NEW
.
Fixes: #18810 (closed)
Topic-rename: FindBoost-allow-root
Edited by Brad King