enable "-fPIC" for CLANG toolchain

[lazydroid]

When trying to use CLANG C++ compiler, the following error is shown, asking to enable "-fPIC" not only for GCC, but for CLANG too:

/usr/bin/ld: src/1.5/libcolladadom150.a(domAny.cpp.o): relocation R_X86_64_PC32 against symbol `_ZN13ColladaDOM1506domAny6createER3DAE' can not be used when making a shared object; recompile with -fPIC

[cielavenir]

@rdiankov could you take a look? We would like to introduce better sanitizer from clang.

[lazydroid]

@yoshikikanemoto could you please take a look?

[cielavenir]

I wonder if yoshiki has privilege on this repo.

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I changed assimp module because I suppose the fork repo does not look accepting pull requests. Now I suppose collada-dom is similar.