[CMake] problem building a qhull project with cmake under cygwin

[LMH]

Hello,

I am trying to compute the convex hull of a high dimensional space (46D x 2000 rows). 
The qhull app available in cygwin/math is based on relatively old code and runs out 
of memory.

I found another version the is supposed to be able to do higher dimensions.

https://bitbucket.org/tomilov/quickhull/src

This version is set up to build with cmake and seems to need clang, so I installed 
both cmake and clang from the cygwin installer. The installed version of cmake is 
3.3.2. If I run clang --version, I don't get any output so I'm not sure what is up 
with that.

At any rate, in cygwin I tried to build the application with ,

cmake ./src

note, I had to copy CMakeLists.txt into the src directory to get this to work. If I 
don't do that, I get the error,

CMake Error: The source directory 
"/cygdrive/g/shared_data/SMD/ATomilov_quickhull/tomilov-quickhull-7faf277d6cc2_cmake/src" 
does not appear to contain CMakeLists.txt.

For what ever reason, the archive downloaded from the bitbucket link above does not 
have CMakeLists.txt file in the src directory but rather on the next level up.

When I have copied the CMakeLists.txt file into ./src, cmake runs but I get the error,

CMake Error at CMakeLists.txt:11 (message):
   only clang supported currently

this comes from the conditional,

if(NOT "${CMAKE_CXX_COMPILER_ID}" MATCHES "Clang")
     message(FATAL_ERROR "only clang supported currently")
endif()

in CMakeLists.txt.

I have installed clang from cygwin, but I still get the same error. I added the 
following line to CMakeLists.txt,

message(STATUS "${CMAKE_CXX_COMPILER_ID}")

and I get "GNU" as the value for CMAKE_CXX_COMPILER_ID, at least that is the value if 
I got the syntax correct for the message statement.

It looks like I need to point CMAKE_CXX_COMPILER_ID to clang, but I am not sure how 
to do that. I don't know if the problem is with the CMakeLists.txt file, the way I am 
calling cmake, or with my local cygwin configuration.

Suggestions would be appreciated.

LMH