Fix test failure by reducing max shm size to 32 MB

Tests are failing on travis because the max allowed SHM size
was set to 2GB. Lowering down to 32 MB.
Also fixing the emulator scripts for mac.

Bug: 73625175
Change-Id: Ia6c3e6df38674c1e4a6723ae87589efe1605c257
diff --git a/src/tracing/core/service_impl.h b/src/tracing/core/service_impl.h
index 65a9ca4..046e983 100644
--- a/src/tracing/core/service_impl.h
+++ b/src/tracing/core/service_impl.h
@@ -54,7 +54,7 @@
 class ServiceImpl : public Service {
  public:
   static constexpr size_t kDefaultShmSize = 256 * 1024ul;
-  static constexpr size_t kMaxShmSize = 4096 * 1024 * 512ul;
+  static constexpr size_t kMaxShmSize = 32 * 1024 * 1024ul;
 
   // The implementation behind the service endpoint exposed to each producer.
   class ProducerEndpointImpl : public Service::ProducerEndpoint {