MSYS2 PATH problems with native compilation (was: msys2 build path problems + copy-paste english results in chinese characters)

[Óscar Fuentes]

Eli Zaretskii <eliz@gnu.org> writes:

>> From: Óscar Fuentes <ofv@wanadoo.es>
>> Date: Thu, 02 Dec 2021 00:01:41 +0100
>> 
>> >>                          Does the directory where you have gas.exe
>> >> appear on the system-wide PATH?
>> >
>> > Nope; I haven't manually added any of msys paths to the system, I thought 
>> > the
>> > build would add some default paths to msys dirs.
>> 
>> Try this in your .emacs :
>> 
>> (let ((dir (file-name-directory (car command-line-args))))
>>   (setenv "PATH" (concat (getenv "PATH") path-separator dir))
>>   (setq exec-path (append exec-path (list dir))))
>
> Changing PATH from within Emacs is not recommended, it will bite you
> down the road when you least expect it.

Revisiting this...

I just checked in the recipe for building Emacs 28.0.90 on MinGW-w64
(MSYS2) with native compilation enabled and found a serious problem.

The Emacs MinGW-w64/MSYS2 package now depends on libgccjit package,
which means that libgccjit will be present when Emacs is installed. But
if Emacs runs without its bin/ directory in PATH, libgccjit is not
functional (an error about missing as.exe is shown.)

Creating a desktop icon for runemacs.exe and starting Emacs from there
is common. Also for MSYS2 users is common to work with multiple
architectures (mingw, clang, ucrt with their 32/64 bits variants)
simultaneously, and putting the binaries of one of those architectures
in global PATH is problematic.

Hence it would be very convenient to use libgccjit without touching PATH.

I ask again: would it be ok to add emacs.exe directory to PATH from
runemacs.exe or emacs.exe itself?

Set PATH for the emacs instances used for generating the .eln files?

Other solution?