CMAKE_BUILD_TYPE case fix

[traceon]

• Do not convert CMAKE_BUILD_TYPE to upper case in-place
  • Causes problems in some generators (Ninja), that construct internal target names based on this value, and sometimes, when this project is included using add_directory(), case mismatch may occur for different references to the same internal targets
  • Not a good idea to modify case in-place, it is just as unsafe as it looks...
• Use CMAKE_CONFIGURATION_TYPES converted to upper case when deducing build type dependent vars
  • CMAKE_C_FLAGS_RelWithDebInfo is not the same as CMAKE_C_FLAGS_RELWITHDEBINFO, so addressed that too here