Ensure that msys2 bin dir is on PATH for bash

[jellespijker]

This should prepend the root directory of msys bin dir, on which the bash.exe
is located, as well as tools such as printenv.

Fixes #11986

Changelog: (Bugfix): Ensure that msys2 bin dir is on PATH for bash
Docs: https://github.com/conan-io/docs/pull/XXXX

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[jellespijker]

@memsharded I think this test might be failing because it doesn't know the all the environmental variables on the PATH in the bash environment. #11981 should take care of that. Do you mind if I merge the branch of that PR into this branch and rerun the tests?

[jellespijker]

@memsharded as @SpaceIm correctly stated, the reported issue happened happened due to to a fault on my msys2 recipe which was missing a bindirs I closed the issue and the PR