The CRT call `getch()` isn't supported on Windows UWP. This function is
used to implement `getpass_r()` for reading a password from the console,
for platforms not supporting it natively. This patch makes this function
a dummy, so password entry from the command-line is no longer supported
for UWP apps. Though it probably did not work before this patch, due to:
CRT headers do declare `getch()`, but it's missing from the CRT DLL.
MSDN documents it as unsupported for UWP:
https://learn.microsoft.com/cpp/c-runtime-library/reference/getchhttps://learn.microsoft.com/cpp/c-runtime-library/reference/getch-getwch
Same is true for the non-deprecated `_getch()` function.
After mingw-w64 synced its implib with `msvcr120_app.dll`, the CI job
`mingw, CM x86_64 schannel R uwp` broke with:
```
[16/16] Linking C executable src\curl.exe
FAILED: src/curl.exe
[...]
D:/a/_temp/msys64/mingw64/bin/../lib/gcc/x86_64-w64-mingw32/14.2.0/../../../../x86_64-w64-mingw32/bin/ld.exe:
src/CMakeFiles/curl.dir/Unity/unity_0_c.c.obj:unity_0_c.c:(.text+0x4d05): undefined reference to `getch'
```
Ref: https://github.com/curl/curl/actions/runs/11873795410/job/33089008727?pr=15597#step:19:25
Also:
- GHA/windows: bump `msys2/setup-msys2` action to
https://github.com/msys2/setup-msys2/commit/c52d1fa
This triggered the build failure above.
Closes#15597
Ref: d408f51e5a/tree/mingw-w64-crt/def-include/crt-aliases.def.inCloses#15637
f988842d85