StackTraceUnix: Add support for arm arch

[akien-mga]

I was positively surprised to see that OD builds almost properly on armv5tl on Mageia; however it fails right at the end when building StackTraceUnix:

[ 99%] Building CXX object CMakeFiles/opendungeons.dir/source/utils/StackTraceUnix.cpp.o
/usr/bin/c++   -DOD_DATA_PATH=\"/usr/share/games/opendungeons\" -DOD_PLUGINS_CFG_PATH=\"/etc/opendungeons\" -DOD_VERSION=\"0.7.0\" -I/home/iurt/rpmbuild/BUILD/opendungeons-0.7.0/source -isystem /usr/include/cegui-0 -isystem /usr/include/OGRE -isystem /usr/include/OIS  -std=c++11  -Wall -Wcast-align -Wcast-qual -Wctor-dtor-privacy -Wdisabled-optimization -Wold-style-cast -Woverloaded-virtual -Wredundant-decls -Wswitch-default -Wstrict-null-sentinel -Winvalid-pch -Wswitch-default -Wstack-protector -O2 -g -pipe -Wformat -Werror=format-security -Wp,-D_FORTIFY_SOURCE=2 -march=armv5t  -DNDEBUG   -Werror -o CMakeFiles/opendungeons.dir/source/utils/StackTraceUnix.cpp.o -c /home/iurt/rpmbuild/BUILD/opendungeons-0.7.0/source/utils/StackTraceUnix.cpp
/home/iurt/rpmbuild/BUILD/opendungeons-0.7.0/source/utils/StackTraceUnix.cpp:112:2: error: #error Unsupported architecture.
 #error Unsupported architecture. // TODO: Add support for other arch.
  ^
/home/iurt/rpmbuild/BUILD/opendungeons-0.7.0/source/utils/StackTraceUnix.cpp: In static member function 'static void StackTracePrintPrivateData::critErrHandler(int, siginfo_t*, void*)':
/home/iurt/rpmbuild/BUILD/opendungeons-0.7.0/source/utils/StackTraceUnix.cpp:105:21: error: unused variable 'uc' [-Werror=unused-variable]
     sig_ucontext_t* uc = static_cast<sig_ucontext_t*>(ucontext);
                     ^

So, opening an issue for this TODO. It would be nice to have support for those arches if it only implies to finding the proper function call in https://github.com/OpenDungeons/OpenDungeons/blob/0.7.0/source/utils/StackTraceUnix.cpp#L107-L113

[akien-mga]

A few lines above we have:

// Prevent running a function that isn't supported on certain platforms.
#if not defined (__i386__) & not defined (__x86_64__)
    std::cout << "No error handler supported for this platform" << std::endl;
    return;
#endif

So I guess it's wrong to make the lack of support for non-x86 platforms a blocking #error.

[akien-mga]

I fixed the arm builds on Mageia with this patch: http://svnweb.mageia.org/packages/cauldron/opendungeons/current/SOURCES/0001-Fix-compilation-of-StackTraceUnix-on-non-x86-platfor.patch?view=markup
It's a bit hackish though, but if it's fine with you as a quick solution I can make a PR :)

[hwoarangmy]

Well, I wouldn't be against removing all the flags for platforms that can be removed (beware of the pointer size). After all, if it is an Unix system, it should work. And it might work for untested platforms (like in this case).