nng-sys: revamp features + discover system NNG #2

	# This workflow checks whether the library is able to run without the std library (e.g., embedded).
	permissions:
	contents: read
	on:
	push:
	branches: [main]
	pull_request:
	concurrency:
	group: ${{ github.workflow }}-${{ github.head_ref \|\| github.run_id }}
	cancel-in-progress: true
	name: no-std
	jobs:
	nostd:
	runs-on: ubuntu-latest
	name: ${{ matrix.target }}
	strategy:
	matrix:
	target: [thumbv7m-none-eabi, aarch64-unknown-none]
	steps:
	- uses: actions/checkout@08c6903cd8c0fde910a37f88322edcfb5dd907a8 # tag=v5.0.0
	with:
	submodules: true
	- name: Install stable
	uses: dtolnay/rust-toolchain@6d653acede28d24f02e3cd41383119e8b1b35921 # branch=master
	with:
	toolchain: stable
	- name: rustup target add ${{ matrix.target }}
	run: rustup target add ${{ matrix.target }}
	- name: cargo check
	run: cargo check --target ${{ matrix.target }} --no-default-features --features vendored

Provide feedback