msys2-runtime: do not forget the MINGW executables when code-signing
msys2-runtime: do not forget the MINGW executables when code-signing

In e03b45ad70 (msys2-runtime: optionally code-sign .exe/.dll files,
2022-01-13), we started to code-sign the `.dll` and `.exe` files when
the environment variable `SIGNTOOL` is set.

But we forgot the MINGW tools (such as `strace.exe`). Let's include
them in the code-signing part.

Signed-off-by: Johannes Schindelin <53fb8db7833fca1e1746dd8592f61048d350f64c@gmx.de>

git-for-windows/MSYS2-packages,git-for-windows/MSYS2-packages,dscho/MSYS2-packages,dscho/MSYS2-packages,dscho/MSYS2-packages,git-for-windows/MSYS2-packages,dscho/MSYS2-packages,git-for-windows/MSYS2-packages