- Miscellaneous CMakeLists.txt fixes.

- fixed a CMake warning about uninitialized use of the variable CROSS_EXPORTS in the tools subfolder when CMAKE_CROSSCOMPILING is off;
- fixed a variable typo: CMAKE_CURRENTY_BINARY_DIR instead of CMAKE_CURRENT_BINARY_DIR;
- in src/CMakeLists.txt, fixed a missing merge of a portion of code from maint branch to master.