fix: vendored OpenSSL for Linux ARM cross-compilation

Add optional `vendored-openssl` feature that compiles OpenSSL from
source during build. Only used in CI for aarch64-unknown-linux-gnu
target where system OpenSSL headers are unavailable.

Default build is unaffected — the feature is not activated.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: Adaimade

.github/workflows/release.yml

@@ -57,7 +57,7 @@ jobs:
 
       - name: Build (cross)
         if: matrix.use_cross
-        run: cross build --release --target ${{ matrix.target }}
+        run: cross build --release --target ${{ matrix.target }} --features vendored-openssl
 
       - name: Build (cargo)
         if: "!matrix.use_cross"

Cargo.lock

@@ -30,6 +30,14 @@ native-tls = "0.2"
 lettre = "0.11"
 rustmem = { git = "https://github.com/Adaimade/R-Mem.git" }
 
+[features]
+vendored-openssl = ["dep:openssl"]
+
+[dependencies.openssl]
+version = "0.10"
+features = ["vendored"]
+optional = true
+
 [profile.release]
 opt-level = "z"
 lto = true