[x265] [PATCH 0 of 3 RFC] further multilib improvements

[Steve Borho]

With these three patches, there is only a single remaining link conflict between the 8bit and 10bit libraries (g_entropyStateBits). To try these, create 8bit/ and 10bit/ folders at the same directory level as an x265 clone (with all my patches applied) then in the 10bit folder run:

cmake ../x265/source -DHIGH_BIT_DEPTH=ON -DEXPORT_C_API=OFF -DENABLE_SHARED=OFF -DENABLE_CLI=OFF
make

Then in the 8bit folder run:
cmake ../x265/source -DEXPORT_C_API=OFF -DENABLE_SHARED=OFF -DENABLE_CLI=ON -DEXTRA_LIB=x265.a
make

you will see that everything builds until the static library link, which fails:

Linking CXX executable x265
duplicate symbol _g_entropyStateBits in:
    libx265.a(entropy.cpp.o)