Add cross-compilation in CI

.github/workflows/checks_and_tests.yml

@@ -40,3 +40,36 @@ jobs:
 
       - name: Run rustdoc for Tokio configuration
         run: cargo doc --features tokio --no-deps
+
+  xcompile:
+    strategy:
+      fail-fast: false
+      matrix:
+        target: [aarch64-linux-android, x86_64-unknown-freebsd]
+        toolchain: ["1.75.0", nightly]
+
+    name: ${{ matrix.toolchain }} on ${{ matrix.target }} (no tests)
+    runs-on: ubuntu-latest
+    env:
+      RUSTFLAGS: --cfg ci
+    steps:
+      - name: Checkout the repository
+        uses: actions/checkout@v4
+
+      - name: Install Rust
+        run: |
+          rustup toolchain install ${{ matrix.toolchain }} --profile minimal --component clippy --no-self-update
+          rustup default ${{ matrix.toolchain }}
+          rustup target add ${{ matrix.target }}
+
+      - name: Run Clippy for default configuration
+        run: cargo clippy --target ${{ matrix.target }} -- -A unknown_lints
+
+      - name: Run rustdoc for default configuration
+        run: cargo doc --target ${{ matrix.target }} --no-deps
+
+      - name: Run Clippy for Tokio configuration
+        run: cargo clippy --target ${{ matrix.target }} --features tokio -- -A unknown_lints
+
+      - name: Run rustdoc for Tokio configuration
+        run: cargo doc --target ${{ matrix.target }} --features tokio --no-deps

README.md

@@ -53,13 +53,22 @@ platform to be demoted, although promotions quite obviously can happen as minor
 	badge if anything is wrong on any of those systems
 -	Certain `#[cfg]`-gated platform-specific features are supported with stable public APIs
 
+##### Explicit support with incomplete CI
+*OSes at this level: **FreeBSD**, **Android***
+
+-	Interprocess is expected to compile and succeed in running all tests – it would be a bug for it
+	not to
+-	GitHub Actions only allows Clippy and Rustdoc to be run for those targets in CI (via
+	cross-compilation) due to a lack of native VMs
+-	Certain `#[cfg]`-gated platform-specific features are supported with stable public APIs
+
 ##### Explicit support without CI
-*OSes at this level: **FreeBSD***
+*OSes at this level: currently none*
 
 -	Interprocess is expected to compile and succeed in running all tests – it would be a bug for it
 	not to
--	Manual testing on local VMs is usually done before every release; CI is not provided solely
-	because GitHub Actions selfishly ignores the existence of those wonderful systems
+-	Manual testing on local VMs is usually done before every release; no CI happens because those
+	targets' standard library `.rlib`s cannot be installed via `rustup target add`
 -	Certain `#[cfg]`-gated platform-specific features are supported with stable public APIs
 
 ##### Support by association