whisper : free backends + fix compile warning

examples/common.h

@@ -181,7 +181,7 @@ private:
     // It is assumed that PCM data is normalized to a range from -1 to 1
     bool write_audio(const float * data, size_t length) {
         for (size_t i = 0; i < length; ++i) {
-            const auto intSample = static_cast<const int16_t>(data[i] * 32767);
+            const int16_t intSample = data[i] * 32767;
             file.write(reinterpret_cast<const char *>(&intSample), sizeof(int16_t));
             dataSize += sizeof(int16_t);
         }