adding assert.h/cassert into samples to be compliant to NDK-r23 (#781)

Author: ggfan

prefab/curl-ssl/app/src/main/cpp/http.cpp

@@ -19,6 +19,7 @@
 #include <memory>
 #include <optional>
 #include <string>
+#include <cassert>
 
 #include "curl/curl.h"
 

teapots/image-decoder/src/main/cpp/Texture.cpp

@@ -16,6 +16,7 @@
 
 #include <GLES3/gl32.h>
 #include <android/data_space.h>
+#include <assert.h>
 
 #include "Texture.h"
 #include <android/imagedecoder.h>