Disable FPU neon optimization on arm64

[kaarrot]

While building on Jetson Nano I got the following error in libPng: [ 82%] Linking CXX executable PDFWriterTestPlayground ../LibPng/libLibPng.a(pngrutil.c.o): In function png_init_filter_functions': pngrutil.c:(.text+0x748c): undefined reference to png_init_filter_functions_neon' collect2: error: ld returned 1 exit status