neovim build needs to be optimized by `CMAKE_BUILD_TYPE=RelWithDebInfo`

Neovim is slow on ARM devices like older version of Raspberry Pi or lg-hammerhead (via PostmarketOS)

Steps:

1. Install neovim
2. Run :checkhealth

Output:

## Performance
  - INFO: Build type: None
  - WARNING: Non-optimized build. Nvim will be slower.
    - ADVICE:
      - Install a different Nvim package, or rebuild with `CMAKE_BUILD_TYPE=RelWithDebInfo`.
      - https://github.com/neovim/neovim/wiki/FAQ

Looks like how it needs to have is update the line 44 at https://git.alpinelinux.org/aports/tree/community/neovim/APKBUILD?id=3bbe716a51a6e39134e91b2787c1bfda419707ef&h=master#n44 with the recommended flag.