PPC_FEATURE_HAS_ALTIVEC is not defined by all C libraries. The following
error was raised while testing SDL3 in Buildroot with a PowerPC toolchain
using uClibc-ng:
src/cpuinfo/SDL_cpuinfo.c: In function 'SDL_GetAltiVecFeatures':
src/cpuinfo/SDL_cpuinfo.c:351:37: error: 'PPC_FEATURE_HAS_ALTIVEC' undeclared (first use in this function)
351 | altivec = getauxval(AT_HWCAP) & PPC_FEATURE_HAS_ALTIVEC;
| ^~~~~~~~~~~~~~~~~~~~~~~
Provide a fallback definition when it is not defined.
Signed-off-by: Dario Binacchi <dario.binacchi@amarulasolutions.com>
e721af3baf