duke3d: build fails on Intel due to use of -faltivec

[ryandesign (Ryan Carsten Schmidt)]

duke3d fails to build.

On OS X 10.11:

​https://paste.macports.org/b9ef383ca46e

make[1]: Entering directory `/opt/local/var/macports/build/_Users_travis_build_macports_macports-ports_games_duke3d/duke3d/work/trunk/source/buildengine'
gcc -c -o build.o build.c -DPLATFORM_MACOSX=1 -faltivec -mdynamic-no-pic -falign-loops=32 -falign-functions=32 -DUDP_NETWORKING=1  -DPLATFORM_UNIX -g -I/opt/local/include/SDL -D_GNU_SOURCE=1 -D_THREAD_SAFE -fno-strict-aliasing -fno-omit-frame-pointer -Wall -O3 -funsigned-char
clang: warning: optimization flag '-falign-loops=32' is not supported
clang: warning: optimization flag '-falign-functions=32' is not supported
clang: error: invalid argument '-faltivec' only allowed with 'ppc/ppc64/ppc64le'
make[1]: *** [build.o] Error 1

On macOS 10.13:

​https://paste.macports.org/97062c73cdc2

make[1]: Entering directory `/opt/local/var/macports/build/_Users_travis_build_macports_macports-ports_games_duke3d/duke3d/work/trunk/source/buildengine'
gcc -c -o build.o build.c -DPLATFORM_MACOSX=1 -faltivec -mdynamic-no-pic -falign-loops=32 -falign-functions=32 -DUDP_NETWORKING=1  -DPLATFORM_UNIX -g -I/opt/local/include/SDL -D_GNU_SOURCE=1 -D_THREAD_SAFE -fno-strict-aliasing -fno-omit-frame-pointer -Wall -O3 -funsigned-char
clang: error: the clang compiler does not support 'faltivec', please use -maltivec and include altivec.h explicitly
clang: warning: optimization flag '-falign-loops=32' is not supported [-Wignored-optimization-argument]
clang: warning: optimization flag '-falign-functions=32' is not supported [-Wignored-optimization-argument]
make[1]: *** [build.o] Error 1

The log also demonstrates that the port isn't UsingTheRightCompiler.

[mf2k (Frank Schima)]

See #56907.

[kencu (Ken)]

The source used in this version of the duke3d port appears to be rather dormant, but this <​http://eduke32.com/> version is more active, and is probably a better option for someone wanting to resurrect this port.

There is also an existing port on freebsd <​https://www.freshports.org/games/eduke32/> that looks like a good starting point.