if we have USE_GPU_PRINTF = TRUE, then fflush the output after burn

this will catch the prints from the burner that were added to
Microphysics

Source/reactions/Castro_react.cpp

@@ -415,8 +415,13 @@ Castro::react_state(MultiFab& s, MultiFab& r, Real time, Real dt, const int stra
         });
 
 #if defined(AMREX_USE_HIP)
-        Gpu::streamSynchronize(); // otherwise HIP may fail to allocate the necessary resources.
+       Gpu::streamSynchronize(); // otherwise HIP may fail to allocate the necessary resources.
+#endif
+
+#ifdef ALLOW_GPU_PRINTF
+       std::fflush(nullptr);
 #endif
+
     }
 
 #if defined(AMREX_USE_GPU)
@@ -812,6 +817,11 @@ Castro::react_state(Real time, Real dt)
 #if defined(AMREX_USE_HIP)
         Gpu::streamSynchronize(); // otherwise HIP may fail to allocate the necessary resources.
 #endif
+
+#ifdef ALLOW_GPU_PRINTF
+       std::fflush(nullptr);
+#endif
+
     }
 
 #if defined(AMREX_USE_GPU)