build: revert to OpenSSL 3.1

OpenSSL 3.2 build currently fails under Nix
so we cannot build deltachat-rpc-server releases:
<alexcrichton/openssl-src-rs#235>

Cargo.toml

@@ -100,6 +100,14 @@ toml = "0.8"
 url = "2"
 uuid = { version = "1", features = ["serde", "v4"] }
 
+# Pin OpenSSL to 3.1 releases.
+# OpenSSL 3.2 has a regression tracked at <https://github.com/openssl/openssl/issues/23376>
+# which results in broken `deltachat-rpc-server` binaries when cross-compiled using Zig toolchain.
+# See <https://github.com/deltachat/deltachat-core-rust/issues/5206> for Delta Chat issue.
+# According to <https://www.openssl.org/policies/releasestrat.html>
+# 3.1 branch will be supported until 2025-03-14.
+openssl-src = "~300.1"
+
 [dev-dependencies]
 ansi_term = "0.12.0"
 anyhow = { version = "1", features = ["backtrace"] } # Enable `backtrace` feature in tests.

flake.nix

@@ -165,6 +165,9 @@
             version = manifest.version;
             strictDeps = true;
             src = pkgs.lib.cleanSource ./.;
+            nativeBuildInputs = [
+              pkgs.perl # Needed to build vendored OpenSSL.
+            ];
             auditable = false; # Avoid cargo-auditable failures.
             doCheck = false; # Disable test as it requires network access.
 
@@ -177,11 +180,6 @@
 
             CC = "${pkgsCross.stdenv.cc}/bin/${pkgsCross.stdenv.cc.targetPrefix}cc";
             LD = "${pkgsCross.stdenv.cc}/bin/${pkgsCross.stdenv.cc.targetPrefix}cc";
-
-            OPENSSL_LIB_DIR = "${pkgsCross.pkgsStatic.openssl.out}/lib";
-            OPENSSL_INCLUDE_DIR = "${pkgsCross.pkgsStatic.openssl.dev}/include";
-            OPENSSL_STATIC = "1";
-            OPENSSL_NO_VENDOR = "1";
           };
 
         mk-aarch64-RustPackage = mkCrossRustPackage "aarch64-unknown-linux-musl" "aarch64-unknown-linux-musl";