feat: add nightly minimum dependencies test

Add a nightly toolchain to test builds using the `-Z
direct-minimum-dependencies` flag. This ensures our minimum version
requirements are compatible with our source code.

This required bumping some versions:

- libc: `0.2.138` -> `0.2.158` as `vsock-rs` depends on `0.2.158`.
- tokio: `1` -> `1.27` as we depend on methods/trait impls which are
  only available starting that version.

This ensures our minimum `tonic` requirement still compiles.

.github/workflows/bvt.yaml

@@ -18,3 +18,29 @@ jobs:
       run: make tokio_vsock
     - name: Build test_server
       run: make test_server
+  bvt-nightly:
+    name: BVT
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v4
+    - name: install dependencies
+      run: |
+        rustup default nightly
+        rustup target add x86_64-unknown-linux-musl
+        rustup component add rustfmt clippy
+    - name: Format Check
+      run: make fmt
+    - name: Clippy Check
+      run: make clippy
+    - name: Build
+      run: make tokio_vsock
+    - name: Build test_server
+      run: make test_server
+    - name: Min deps build
+      run: |
+        rm Cargo.lock
+        cargo build --features tonic-conn --lib -Z direct-minimal-versions
+    - name: Normal build
+      run: |
+        rm Cargo.lock
+        cargo build --features tonic-conn --lib

Cargo.toml

@@ -16,15 +16,15 @@ tonic-conn = ["tonic"]
 [dependencies]
 bytes = "1.3.0"
 futures = "0.3"
-libc = "0.2.138"
+libc = "0.2.158"
 vsock = "0.5.1"
-tokio = { version = "1", features = ["net", "sync"] }
+tokio = { version = "1.27", features = ["net", "sync"] }
 tonic = { version = ">= 0.5.0, < 0.13.0", optional = true }
 
 [dev-dependencies]
 sha2 = "0.10.6"
 rand = "0.8.5"
-tokio = { version = "1", features = ["macros", "rt", "io-util"] }
+tokio = { version = "1.27", features = ["macros", "rt", "io-util"] }
 
 [package.metadata.docs.rs]
 all-features = true