Cleanup: use lowercase cmake commands

The `Find*.cmake` modules originally used uppercase commands to match
CMake's own conventions. Since then CMake uses lower-case and even
within our own find modules, using all uppercase wasn't done
consistently. Opt for lowercase everywhere.

tests/python/CMakeLists.txt

@@ -632,7 +632,7 @@ if(WITH_CYCLES OR WITH_OPENGL_RENDER_TESTS)
             -blacklist ${_cycles_blacklist}
           )
 
-          if(NOT("${_cycles_device_lower}" STREQUAL "cpu"))
+          if(NOT ("${_cycles_device_lower}" STREQUAL "cpu"))
             set_tests_properties(${_cycles_test_name} PROPERTIES RUN_SERIAL TRUE)
           endif()
           unset(_cycles_test_name)
@@ -870,7 +870,7 @@ endif()
 if(NOT OPENIMAGEIO_IDIFF)
   message(STATUS "Disabling ImBuf image format tests because OIIO idiff does not exist")
 else()
-  SET(OPTIONAL_FORMATS "")
+  set(OPTIONAL_FORMATS "")
   if(WITH_IMAGE_CINEON)
     set(OPTIONAL_FORMATS "${OPTIONAL_FORMATS} CINEON")
   endif()