In commit v3.11.0-rc1~466^2 (Compiler/TI: Add support for depfile
generation for Ninja, 2017-10-16) the flag for C++ was added in a
variable with a typo in its name. Fix the spelling.
Issue: #17360
Teach the Makefile and Ninja generators to substitute for an <INCLUDES>
placeholder instead of putting -I in <FLAGS>. Update our values for
CMAKE_<LANG>_COMPILE_OBJECT,
CMAKE_<LANG>_CREATE_ASSEMBLY_SOURCE, and
CMAKE_<LANG>_CREATE_PREPROCESSED_SOURCE
to place <INCLUDES> just before <FLAGS>.