In line 2751 of tcl.m4 there is a check like:

*win32*|*WIN32*|*MINGW32_*|*MINGW64_*)

This does not include MSYS_NT-10.0. The line should be changed to:

*win32*|*WIN32*|*MINGW32_*|*MINGW64_*|*MSYS_NT*)

MSYS_NT-* will appear if you install MSYS2, but do not install gcc, because you want to use autotools/make with Visual Studio compiler.
In such a case, you run the vcvarsal.bat script, to get a command prompt with the visual studio compiler tools, and then you run bash in that command prompt.

Like:

%comspec% /K "C:\Program Files (x86)\Microsoft Visual && set "MSYS2_PATH_TYPE=inherit" && --login

Then uname -s returns MSYS_NT-10.0.