some functions are hideen by macros. for example `getentropy` is hidden by [__BSD_VISIBLE](https://github.com/vitasdk/newlib/blob/vita/newlib/libc/include/sys/unistd.h#L106-L108) to export functions like [phoenix platform](https://github.com/vitasdk/newlib/blob/vita/newlib/libc/sys/phoenix/sys/unistd.h), we have to create or copy & modify this file. it releated vitasdk/packages#273
some functions are hideen by macros.
for example
getentropyis hidden by __BSD_VISIBLEto export functions like phoenix platform, we have to create or copy & modify this file.
it releated vitasdk/packages#273