Cygwin: Stable minimal `bash.exe`

[Blackhex]

Description

Provide native bash.exe build with minimum set of features supported which on the other hand supports most of the MinGit use-cases, stable enough to be included in #266.

Depencencies

• #287

Acceptance criteria

• Fork of the upstream source code repository of Bash with Windows-on-Arm64-specific changes applied can be built with minimum set of dependencies and configurations on Linux outside of the MSYS2 build system using aarch64-pc-cygwin cross-compilation toolchain that includes minimal required set of POSIX APIs implementations.
• The quality of such build is comparable to aarch64-pc-linux-gnu and x86_64-pc-cygwin target builds in terms of the percentage of passing tests from the upstream Bash test suite limited to the supported feature set.
• ncurses and readline are supported, SSH is not supported.