cmake: updated to 3.12.2

Changes in 3.12.2 since 3.12.1:
* Android: Add support for NDK r18
* CheckIPOSupported: Simplify result reporting logic
* CheckIPOSupported: Tolerate backslashes in output of failed checks
* VS: Restore CMakeLists.txt references in each target
* EXPORT_PROPERTIES: Add test for an undefined property
* EXPORT_PROPERTIES: Prevent null dereference for undefined property
* Help: Fix typo in clang-tidy example -checks option
* FindBoost: Fix context discovery for 1.60 and below
* FindCUDA: Do not find cublas_device on CUDA >= 9.2
* FindMatlab: Remove erroneous duplicate code
* CUDA: Avoid using deprecated cublas_device to identify device lib dirs
* cmState: Clear GlobVerificationManager state on Reset

(adam)