bug#60966: 30.0.50; Emacs -nw on msys2 is not clearing the terminal

[Ergus via "Bug reports for GNU Emacs, the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>]

On Tue, Jan 24, 2023 at 03:16:46PM +0200, Eli Zaretskii wrote:
>> Date: Mon, 23 Jan 2023 22:45:15 +0000 (UTC)
>> From: Ergus <spacibba@aol.com>
>> Cc: "60966@debbugs.gnu.org" <60966@debbugs.gnu.org>
>>
>> Thanks, now I understand the problem... it is a bit weird, but OK.
>
>Please tell what you understood and what you think is weird.  I'd like
>to make sure there's no misunderstanding here.
>
Hi Eli:

It is just a bit weird that emacs shouldn't be called from within the
msys terminal, maybe a warning message or something may help here. It is
not terrible, just a bit confusing.

>> Today I also tried the nt/INSTALL.64 steps and somehow I got an issue about #include <ms-w32.h>: No
>> such file or directory.
>>
>> I repeated the steps in the guide carefully but I only get the same error after make.
>>
>> ---------------------------------
>>
>> In file included from ../src/config.h 3043
>>
>> ../../source/lib/../src/conf_post.h:38:11: fatal error: ms-w32.h: No such file or directory
>>    38 | # include <ms-w32.h>
>>         |
>> compilation terminated
>
>Please show the full compilation command, it sounds like some compiler
>switches might be missing.  You can request display of full commands
>during the build if you say
>
>   make V=1
>
>The configure script arranges for MinGW builds to add the -I../nt/inc
>option to the compilation command line, which is where the ms-w32.h
>header lives.

I tried this and I see that the -I line is added correctly, but the
directory where I am building is inside 'Documents and Settings' which
has spaces and I don't see any quote or \ escape.

gcc -c -mtune=generic -DUSE_CRT_DLL=1 -I /c/Documents and
Settings/T008593/Downloads/emacs/build/../source/nt/inc -mtune=generic
-MMD -MF deps/fingerprint.d -MP -g3 -O2 -gdwarf-2 -I. -I../src
-I../../source/lib -I../../source/lib/../src -DGL_COMPILE_CRYPTO_STREAM
-o fingerprint.o ../../source/lib/fingerprint.c

So, probably is this the problem??

>> Any idea? I am using the mingw64 terminal to build as the guide says... so maybe there is anything wrong in
>> my envirnment?
>
>If the above doesn't help, tell me how you configured the build: which
>configure command you used and in whether your build is in the source
>directory or outside of it.  Also, if you previously did another build
>in the same tree, you need to clean the tree ("make extraclean").

Just to mention, the build is outside of sources. I made all the clean
as usual like on GNU/Linux.

Thanks,
Ergus