add ability for consumers to specify env file / log info & continue if not exists

lambdabuild.zig

@@ -16,6 +16,10 @@ pub const Config = struct {
 
     /// Default IAM role name if not specified via -Drole-name.
     default_role_name: []const u8 = "lambda_basic_execution",
+
+    /// Default environment file if not specified via -Denv-file.
+    /// If the file doesn't exist, it's silently skipped.
+    default_env_file: ?[]const u8 = ".env",
 };
 
 /// Information about the configured Lambda build steps.
@@ -84,7 +88,7 @@ pub fn configureBuild(
         []const u8,
         "env-file",
         "Path to environment variables file (KEY=VALUE format)",
-    ) orelse null;
+    ) orelse config.default_env_file;
     const allow_principal = b.option(
         []const u8,
         "allow-principal",

tools/build/src/deploy.zig

@@ -138,8 +138,12 @@ fn loadEnvFile(
     allocator: std.mem.Allocator,
 ) !void {
     const file = std.fs.cwd().openFile(path, .{}) catch |err| {
+        if (err == error.FileNotFound) {
+            std.log.info("Env file '{s}' not found, skipping", .{path});
+            return;
+        }
         std.log.err("Failed to open env file '{s}': {}", .{ path, err });
-        return error.EnvFileNotFound;
+        return error.EnvFileOpenError;
     };
     defer file.close();