Fix issues running DeepSpeech

[doe300]

See doe300/VC4CL#31 for discussion:

• Switch to LLVM library front-end as recommended front-end
• Fix wrong parsing of parameters in LLVM library front-end (Duplicate parameter for method: i32 % and Not all path generate a valid value for local:)
• SPIRV-LLVM creates empty VC4CLStdLib.bc (see also Replace eraseUselessFunctions with a more specific one KhronosGroup/SPIRV-LLVM#14 and the functions here and here)
• Fix the error failing to inline float4 vload4(size_t, <some qualifiers> float*)

[doe300]

SPIRV-LLVM is deprecated in favor of SPIRV-LLVM-Translator which does not generate an LLVM module at all, but uses the "default" LLVM/Clang to do so