FANN fails to build with CMake 4

[NHOrus]

CMake 4 raised minimum compatible version to CMake 3.5.
See https://gitlab.kitware.com/cmake/cmake/-/issues/26698 and https://gitlab.kitware.com/cmake/cmake/-/issues/26613

See also https://bugs.gentoo.org/951922

[NHOrus]

See https://github.com/gentoo/gentoo/pull/41260/files#diff-022c94435aba74f1941bd0d576918867a1c73e31c7948276ab1c7ea6399342f8 for a patch for 2.2.0

[NHOrus]

For current version from git, gtest subprojects need patching, too. Or removal as bundled dependency.