silence sprintf deprecated warnings and enable imwri in macos build

[yuygfgg]

MacOS clang compiler complains about

src/core/vscore.cpp:1496:13: warning: 'sprintf' is deprecated: This function is provided for compatibility reasons only.  Due to security concerns inherent in the design of sprintf(3), it is highly recommended that you use snprintf(3) instead. [-Wdeprecated-declarations]
 1496 |             sprintf(suffix, "%d", (colorFamily == vs3::cmRGB ? 3:1) * bitsPerSample);
      |             ^
/Library/Developer/CommandLineTools/SDKs/MacOSX14.sdk/usr/include/stdio.h:180:1: note: 'sprintf' has been explicitly marked deprecated here
  180 | __deprecated_msg("This function is provided for compatibility reasons only.  Due to security concerns inherent in the design of sprintf(3), it is highly recommended that you use snprintf(3) instead.")
      | ^
/Library/Developer/CommandLineTools/SDKs/MacOSX14.sdk/usr/include/sys/cdefs.h:[21](https://github.com/yuygfgg/vapoursynth-classic/actions/runs/10958658371/job/30429337951#step:10:22)8:48: note: expanded from macro '__deprecated_msg'
  218 |         #define __deprecated_msg(_msg) __attribute__((__deprecated__(_msg)))
      |                                                       ^
src/core/vscore.cpp:1856:9: warning: 'sprintf' is deprecated: This function is provided for compatibility reasons only.  Due to security concerns inherent in the design of sprintf(3), it is highly recommended that you use snprintf(3) instead. [-Wdeprecated-declarations]
 1856 |         sprintf(suffix, "%d", (format.colorFamily == cfRGB ? 3:1) * format.bitsPerSample);
      |         ^
/Library/Developer/CommandLineTools/SDKs/MacOSX14.sdk/usr/include/stdio.h:180:1: note: 'sprintf' has been explicitly marked deprecated here
  180 | __deprecated_msg("This function is provided for compatibility reasons only.  Due to security concerns inherent in the design of sprintf(3), it is highly recommended that you use snprintf(3) instead.")
      | ^
/Library/Developer/CommandLineTools/SDKs/MacOSX14.sdk/usr/include/sys/cdefs.h:218:48: note: expanded from macro '__deprecated_msg'
  218 |         #define __deprecated_msg(_msg) __attribute__((__deprecated__(_msg)))

[WolframRhodium]

Thanks!