CMake: quiet uninitialized warnings

CMakeLists.txt

build_files/cmake/Modules/FindLevelZero.cmake

build_files/cmake/Modules/FindOSL.cmake

build_files/cmake/Modules/FindUSD.cmake

build_files/cmake/platform/platform_apple.cmake

build_files/cmake/platform/platform_unix.cmake

extern/CMakeLists.txt

intern/cycles/cmake/macros.cmake

intern/eigen/CMakeLists.txt

source/blender/draw/CMakeLists.txt

source/blender/editors/curves/CMakeLists.txt

source/blender/editors/mesh/CMakeLists.txt

source/blender/editors/render/CMakeLists.txt

source/blender/editors/sculpt_paint/CMakeLists.txt

source/blender/editors/space_node/CMakeLists.txt

source/blender/geometry/CMakeLists.txt

source/blender/nodes/CMakeLists.txt

source/blender/nodes/geometry/CMakeLists.txt

source/blender/nodes/shader/CMakeLists.txt

source/blender/simulation/CMakeLists.txt