[CMake] Not finding build type when using cmake with llvm/clang

[Edward Diener]

When trying to build llvm/clang on Windows using cmake I execute from a 
build directory I created:

cmake -DCMAKE_BUILD_TYPE=Release -G "MinGW Makefiles" ..\llvm

only to receive:

CMake Error: CMake was unable to find a build program corresponding to 
"MinGW Makefiles".  CMAKE_MAKE_PROGRAM is not set.  You probably need to 
select a different build tool.
CMake Error: CMake was unable to find a build program corresponding to 
"MinGW Makefiles".  CMAKE_MAKE_PROGRAM is not set.  You probably need to 
select a different build tool.
CMake Error: Error required internal CMake variable not set, cmake may 
be not be built correctly.
Missing variable is:
CMAKE_C_COMPILER_ENV_VAR
CMake Error: Error required internal CMake variable not set, cmake may 
be not be built correctly.
Missing variable is:
CMAKE_C_COMPILER
CMake Error: Could not find cmake module file: 
C:/Programming/VersionControl/bmw64_clang/CMakeFiles/2.8.12.1/CMakeCCompiler.cmake
CMake Error: Error required internal CMake variable not set, cmake may 
be not be built correctly.
Missing variable is:
CMAKE_CXX_COMPILER_ENV_VAR
CMake Error: Error required internal CMake variable not set, cmake may 
be not be built correctly.
Missing variable is:
CMAKE_CXX_COMPILER
CMake Error: Could not find cmake module file: 
C:/Programming/VersionControl/bmw64_clang/CMakeFiles/2.8.12.1/CMakeCXXCompiler.cmake
CMake Error: CMAKE_C_COMPILER not set, after EnableLanguage
CMake Error: CMAKE_CXX_COMPILER not set, after EnableLanguage
-- Configuring incomplete, errors occurred!
See also 
"C:/Programming/VersionControl/bmw64_clang/CMakeFiles/CMakeOutput.log".
See also 
"C:/Programming/VersionControl/bmw64_clang/CMakeFiles/CMakeError.log".

I am using cmake 2.8.12.1. The doc says that "MinGW Makefiles" is a 
valid build type.

Why is cmake looking for and why is i failing ?

If I use "Ninja" as the build type cmake works fine.