I managed to compile Eigen_demo in Debug ...

$ wine umk reference Eigen_demo CLANGx64 -bu
----- Core ( CLANG DEBUG DEBUG_FULL BLITZ WIN32 ) (1 / 4)
----- plugin/Eigen ( CLANG DEBUG DEBUG_FULL BLITZ WIN32 ) (2 / 4)
----- plugin/z ( CLANG DEBUG DEBUG_FULL BLITZ WIN32 ) (3 / 4)
----- Eigen_demo ( MAIN CLANG DEBUG DEBUG_FULL BLITZ WIN32 ) (4 / 4)
BLITZ: eigen_demo.cpp non-linear.cpp fft.cpp
Eigen_demo: 3 file(s) built in (37:40.15), 753384 msecs / file
Linking...
Z:\home\ssg\.local\soft\bb-worker\worker\wine-upp\build\.cache\upp.out\CLANGx64.Debug.Debug_Full\Eigen_demo.exe (6637568 B) linked in (0:01.46)

OK. (37:42.11)

Less than 40 minutes

----- Eigen_demo ( MAIN CLANG DEBUG DEBUG_FULL WIN32 ) (4 / 4)
eigen_demo.cpp
non-linear.cpp
fft.cpp
Eigen_demo: 3 file(s) built in (20:14.75), 404918 msecs / file
Linking...
Z:\home\ssg\.local\soft\bb-worker\worker\wine-upp\build\.cache\upp.out\CLANGx64.Debug.Debug_Full.Noblitz\Eigen_demo.exe (6253568 B) linked in (0:01.40)

OK. (21:47.23)