Okay, I've got something here.

The compiler errors are only about those gmtime_r and strtok_r declarations. I just commented out these two declarations in <utility.h> and built my project again. It compiles without errors. Apparently, the C library now defines these two functions.

Digging a little deeper into <time.h> from the toolchain bundled with Qt, I found this for gmtime_r:
Qt Code: 
  1. #ifndef gmtime_r
  2. #define gmtime_r(_Time,_Tm) ...
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<pthread.h> contains the same thing for strtok_r. Was this added to the C library recently?