cabana: set the COMMA_CACHE environment variable (#29849)

* set COMMA_CACHE enviroment

* use /tmp/comma_donwloand_cache

tools/cabana/streams/replaystream.cc

@@ -8,10 +8,13 @@
 
 ReplayStream::ReplayStream(QObject *parent) : AbstractStream(parent) {
   unsetenv("ZMQ");
+  setenv("COMMA_CACHE", "/tmp/comma_download_cache", 1);
+
   // TODO: Remove when OpenpilotPrefix supports ZMQ
 #ifndef __APPLE__
   op_prefix = std::make_unique<OpenpilotPrefix>();
 #endif
+
   QObject::connect(&settings, &Settings::changed, [this]() {
     if (replay) replay->setSegmentCacheLimit(settings.max_cached_minutes);
   });