MinGW C compiler "not able to compile a simple test program" - makefile

Question

I want to run MinGW as a C compiler. MinGW has been installed from Chocolatey. Invocation is from gitlab-runner through CMake. This fails with
$ cmake -G "MinGW Makefiles" -DCMAKE_C_COMPILER=x86_64-w64-mingw32-gcc -DLIB_MAN=OFF -DCMAKE_INSTALL_PREFIX=C:\opt\x64 -B. ..
-- The C compiler identification is unknown
-- Check for working C compiler: C:/ProgramData/chocolatey/bin/x86_64-w64-mingw32-gcc.exe
-- Check for working C compiler: C:/ProgramData/chocolatey/bin/x86_64-w64-mingw32-gcc.exe -- broken
CMake Error at C:/Program Files/CMake/share/cmake-3.16/Modules/CMakeTestCCompiler.cmake:60 (message):
The C compiler
"C:/ProgramData/chocolatey/bin/x86_64-w64-mingw32-gcc.exe"
is not able to compile a simple test program.
It fails with the following output:
Change Dir: C:/gitlab-runner/builds/zjE1Mkfg/0/mlz/kww/build/CMakeFiles/CMakeTmp
Run Build Command(s):C:/ProgramData/chocolatey/bin/mingw32-make.exe cmTC_ffa53/fast && C:/ProgramData/chocolatey/lib/mingw/tools/install/mingw64/bin/mingw32-make -f CMakeFiles\cmTC_ffa53.dir\build.make CMakeFiles/cmTC_ffa53.dir/build
mingw32-make[1]: Entering directory 'C:/gitlab-runner/builds/zjE1Mkfg/0/mlz/kww/build/CMakeFiles/CMakeTmp'
Building C object CMakeFiles/cmTC_ffa53.dir/testCCompiler.c.obj
C:\ProgramData\chocolatey\bin\x86_64-w64-mingw32-gcc.exe -o CMakeFiles\cmTC_ffa53.dir\testCCompiler.c.obj -c C:\gitlab-runner\builds\zjE1Mkfg\0\mlz\kww\build\CMakeFiles\CMakeTmp\testCCompiler.c
mingw32-make[1]: *** [CMakeFiles\cmTC_ffa53.dir\build.make:65: CMakeFiles/cmTC_ffa53.dir/testCCompiler.c.obj] Error 1
mingw32-make[1]: Leaving directory 'C:/gitlab-runner/builds/zjE1Mkfg/0/mlz/kww/build/CMakeFiles/CMakeTmp'
mingw32-make: *** [Makefile:120: cmTC_ffa53/fast] Error 2
CMake will not be able to correctly generate this project.
Call Stack (most recent call first):
CMakeLists.txt:6 (project)
-- Configuring incomplete, errors occurred!
See also "C:/gitlab-runner/builds/zjE1Mkfg/0/mlz/kww/build/CMakeFiles/CMakeOutput.log".
See also "C:/gitlab-runner/builds/zjE1Mkfg/0/mlz/kww/build/CMakeFiles/CMakeError.log".
ERROR: Job failed: exit status 1
From various web sources I understand that MinGW is bound to fail if sh.exe is present on the system [1]. However, sh.exe comes with several applications, among them Git and Visual Studio, which I cannot remove. Somewhere it's suggested to add -DCMAKE_SH="CMAKE_SH-NOTFOUND", which, however, has no effect.
I've seen a related question from 2015 [2], which however involves CLion. The only upvoted answer contains several broken links - altogether, that thread isn't helpful.
How to proceed? Is there a chance to work around the sh.exe problem?
Other advice on the web suggests to use -G "MSYS Makefiles". However, the CMake documentation [3] seems to rule this out: "not compatible with a Windows command prompt. To build under a Windows command prompt, use the MinGW Makefiles generator."
[1] https://stackoverflow.com/a/7411982/1017348
[2] CLion: Error:The C compiler "C:/MinGW/bin/gcc.exe" is not able to compile a simple test program
[3] https://cmake.org/cmake/help/latest/generator/MSYS%20Makefiles.html#generator:MSYS%20Makefiles per CMake 3.16.1

Answer 1

After long experimentation, I conclude that the problem comes from Chocolatey's packaging of MinGW. The problem is gone after I
uninstalled the MinGW package from Chocolatey,
reinstalled MinGW using the original MinGW installer,
installed the Ninja Chocolatey package,
inserted C:\MinGW\bin on top of PATH.
$ cmake -G "Ninja" -DLIB_MAN=OFF -DCMAKE_INSTALL_PREFIX=C:\opt\x64 -B. ..
-- The C compiler identification is GNU 8.2.0
-- Check for working C compiler: C:/MinGW/bin/gcc.exe
-- Check for working C compiler: C:/MinGW/bin/gcc.exe -- works
Also note:
There is no need for -DCMAKE_C_COMPILER=...
I did not try hard to get -G "MinGW Makefile" working; -G Ninja works just fine.

Answer 2

The sh.exe is only a problem when you run CMake the first time when trying to generate the project. You can rerun CMake again and CMake will continue with normal processing to generate the project (tested in version 3.16). I saw a patch that removes this check and should be part of a future release of CMake.
It's already mentioned that gcc is installed incorrectly. That always seems to be the case when anyone mentions that gcc fails with an Error 1 message. It should be noted that Error 1 is not from CMake. CMake is just gathering the output from when it runs mingw32-make to build the sample project.
The first message in the output -- The C compiler identification is unknown is a pretty clear message that your compiler isn't working. All of the output for this step is in the log and error files that CMake generates in the build folder. You'll be able to see how it invoked the compiler and with which options and the output from the compiler.