`color_uquant_to_scrambled_pquant_tables` not defined for decompress only build

[王少东 (Shaodong Wang)]

The definition of color_uquant_to_scrambled_pquant_tables is guarded by #if !defined(ASTCENC_DECOMPRESS_ONLY) #endif but used in astcenc_symbolic_physical.cpp unguarded. v4.3.1

[Pete Harris]

Thanks for the bug report. The Release build we have in CI wasn't failing because LTO was stripping out the dead code before linkage fails.