CMake scripts fail to detect Arm - cannot build aarch64 out of the box

[dslarm]

With GCC and Rocky-9 Linux, and cmake 3.26.5, the path for building pufferfish on Arm is not being followed.

Adding a 'message' to dump out the CMAKE_SYSTEM_PROCESSOR shows it to be empty at the point of the if statement in CMakeLists.txt.

According to: https://stackoverflow.com/questions/51024294/cmake-system-processor-seems-to-be-empty-whats-the-best-strategy-for-os-agnost - this value is only set after the project() declaration. However, Pufferfish puts this logic before the "project" declaration.

Fix: move the project("pufferfish") to line 1 of CMakeLists.txt.