openssl support depend on ZAP_USE_OPENSSL=true env

build.zig

@@ -7,7 +7,13 @@ pub fn build(b: *std.build.Builder) !void {
     // between Debug, ReleaseSafe, ReleaseFast, and ReleaseSmall.
     const optimize = b.standardOptimizeOption(.{});
 
-    const use_openssl = b.option(bool, "openssl", "Use system-installed openssl for TLS support in zap") orelse false;
+    // Use an os env var to determine whether to build openssl support
+    const use_openssl = blk: {
+        if (std.os.getenv("ZAP_USE_OPENSSL")) |val| {
+            if (std.mem.eql(u8, val, "true")) break :blk true;
+        }
+        break :blk false;
+    };
 
     // create a module to be used internally.
     var zap_module = b.createModule(.{