Fix GCC 12 -Wrestrict warning in util.cpp (argv_to_string/join)

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

mac/util.cpp

@@ -229,7 +229,10 @@ std::string join(int argc, char* argv[], const std::string& separator)
 {
     std::string result {};
     for (int i = 0; i < argc; ++i) {
-        result += std::string(argv[i]) + separator;
+        // Append directly (see argv_to_string): avoids a temporary and the same
+        // GCC 12 -Wrestrict false positive.
+        result += argv[i];
+        result += separator;
     }
     return result;
 }
@@ -241,7 +244,11 @@ std::string argv_to_string(int argc, char* argv[])
     }
     std::string result = argv[0];
     for (int i = 1; i < argc; ++i) {
-        result += " " + std::string(argv[i]);
+        // Append the pieces directly rather than building a `" " + string(...)`
+        // temporary: identical result, avoids an allocation, and sidesteps a
+        // GCC 12 -Wrestrict false positive on the temporary's memcpy.
+        result += ' ';
+        result += argv[i];
     }
     return result;
 }