GCC/Linux support

[neobenedict]

https://github.com/SergeyMakeev/Goofy/blob/master/GoofyTC/goofy_tc.h#L1453

blRangeY.m128i_u8[0] is not available outside MSVC.

Possible replacement (and I am no expert in using processor intrinsics):

alignas(16) unsigned char m128i_u8[16];
_mm_storeu_si128((__m128i*)m128i_u8, blRangeY);

const uint32_t block0a = etc1BrighnessRangeTocontrolByte[m128i_u8[0]] | ((baseColors.r0 << 3ull) & 0xFFFFFF);

Seems to work OK for me.

Some other things needed

#if defined(__GNUC__) || defined(__clang__)
#  define ALIGN(x) __attribute__ ((aligned(x)))
# define goofy_inline __attribute__((always_inline)) inline
#  define goofy_restrict __restrict
#elif defined(_MSC_VER)
#  define ALIGN(x) __declspec(align(x))
#  define goofy_restrict __restrict
#  define goofy_inline __forceinline
#else
#  error "Unknown compiler; can't define ALIGN"
#endif

    // constants
    ALIGN(16) static const uint32_t gConstEight[4] = { 0x08080808, 0x08080808, 0x08080808, 0x08080808 };
    ALIGN(16) static const uint32_t gConstSixteen[4] = { 0x10101010, 0x10101010, 0x10101010, 0x10101010 };
    ALIGN(16) static const uint32_t gConstMaxInt[4] = { 0x7f7f7f7f, 0x7f7f7f7f, 0x7f7f7f7f, 0x7f7f7f7f };

Possibly also x86intrin.h instead of immintrin.h

Also, the program completely fails if compressETC1 is not wrapped in #pragma optimize( "", off ).