Rewrite the swiftc params file if an argument contains a space.

Bazel does not quote arguments when it writes a multiline params file, but LLVM's command line parser does not distinguish between newlines and other kinds of whitespace, and we don't want to use the shell-quoted params file format from Bazel because it would be more difficult for us to parse. This change ensures that if a line in the incoming params file contains a space, it causes a rewrite which triggers the defensive "quote everything" logic.

RELNOTES: None.
PiperOrigin-RevId: 307876851

tools/worker/swift_runner.cc

@@ -203,7 +203,11 @@ bool SwiftRunner::ProcessArgument(
     // Apply any other text substitutions needed in the argument (i.e., for
     // Apple toolchains).
     auto new_arg = arg;
-    changed = MakeSubstitutions(&new_arg, bazel_placeholder_substitutions_);
+    // Bazel doesn't quote arguments in multi-line params files, so we need to
+    // ensure that our defensive quoting kicks in if an argument contains a
+    // space, even if no other changes would have been made.
+    changed = MakeSubstitutions(&new_arg, bazel_placeholder_substitutions_) ||
+              new_arg.find_first_of(' ') != std::string::npos;
     consumer(new_arg);
   }