SwitfShader + DXC build failure

[jaebaek]

We want to test HLSL shaders using SwiftShader.
When I build Amber witht the following command, I met linking errors:

mkdir -p out/SWFT && cd out/SWFT
cmake -GNinja -DAMBER_USE_DXC=true -DAMBER_ENABLE_SWIFTSHADER=TRUE -DAMBER_USE_LOCAL_VULKAN=true ../..
ninja

/usr/bin/ld: /usr/local/home/jaebaek/sdb/amber.git/out/SWFT/../../third_party/dxc/lib/DxcSupport/HLSLOptions.cpp:274: undefined reference to `llvm::opt::ArgList::getLastArgValue(llvm::opt::OptSpecifier, llvm::StringRef) const'
/usr/bin/ld: third_party/dxc/lib/libLLVMDxcSupport.a(HLSLOptions.cpp.o): in function `hlsl::options::ReadDxcOpts(llvm::opt::OptTable const*, unsigned int, hlsl::options::MainArgs const&, hlsl::options::DxcOpts&, llvm::raw_ostream&)':
/usr/local/home/jaebaek/sdb/amber.git/out/SWFT/../../third_party/dxc/lib/DxcSupport/HLSLOptions.cpp:323: undefined reference to `llvm::opt::OptTable::ParseArgs(llvm::ArrayRef<char const*>, unsigned int&, unsigned int&, unsigned int, unsigned int) const'
/usr/bin/ld: /usr/local/home/jaebaek/sdb/amber.git/out/SWFT/../../third_party/dxc/lib/DxcSupport/HLSLOptions.cpp:327: undefined reference to `llvm::opt::ArgList::getLastArgValue(llvm::opt::OptSpecifier, llvm::StringRef) const'
/usr/bin/ld: /usr/local/home/jaebaek/sdb/amber.git/out/SWFT/../../third_party/dxc/lib/DxcSupport/HLSLOptions.cpp:341: undefined reference to `llvm::opt::ArgList::getLastArgValue(llvm::opt::OptSpecifier, llvm::StringRef) const'
/usr/bin/ld: /usr/local/home/jaebaek/sdb/amber.git/out/SWFT/../../third_party/dxc/lib/DxcSupport/HLSLOptions.cpp:342: undefined reference to `llvm::opt::ArgList::getLastArgValue(llvm::opt::OptSpecifier, llvm::StringRef) const'
/usr/bin/ld: /usr/local/home/jaebaek/sdb/amber.git/out/SWFT/../../third_party/dxc/lib/DxcSupport/HLSLOptions.cpp:358: undefined reference to `llvm::opt::ArgList::hasFlag(llvm::opt::OptSpecifier, llvm::opt::OptSpecifier, bool) const'
/usr/bin/ld: /usr/local/home/jaebaek/sdb/amber.git/out/SWFT/../../third_party/dxc/lib/DxcSupport/HLSLOptions.cpp:359: undefined reference to `llvm::opt::ArgList::hasFlag(llvm::opt::OptSpecifier, llvm::opt::OptSpecifier, bool) const'
/usr/bin/ld: /usr/local/home/jaebaek/sdb/amber.git/out/SWFT/../../third_party/dxc/lib/DxcSupport/HLSLOptions.cpp:372: undefined reference to `llvm::opt::Arg::getAsString[abi:cxx11](llvm::opt::ArgList const&) const'
/usr/bin/ld: /usr/local/home/jaebaek/sdb/amber.git/out/SWFT/../../third_party/dxc/lib/DxcSupport/HLSLOptions.cpp:389: undefined reference to `llvm::opt::ArgList::hasFlag(llvm::opt::OptSpecifier, llvm::opt::OptSpecifier, bool) const'
/usr/bin/ld: /usr/local/home/jaebaek/sdb/amber.git/out/SWFT/../../third_party/dxc/lib/DxcSupport/HLSLOptions.cpp:390: undefined reference to `llvm::opt::ArgList::getLastArgValue(llvm::opt::OptSpecifier, llvm::StringRef) const'
/usr/bin/ld: /usr/local/home/jaebaek/sdb/amber.git/out/SWFT/../../third_party/dxc/lib/DxcSupport/HLSLOptions.cpp:395: undefined reference to `llvm::opt::ArgList::getLastArgValue(llvm::opt::OptSpecifier, llvm::StringRef) const'
/usr/bin/ld: /usr/local/home/jaebaek/sdb/amber.git/out/SWFT/../../third_party/dxc/lib/DxcSupport/HLSLOptions.cpp:404: undefined reference to `llvm::opt::ArgList::getLastArg(llvm::opt::OptSpecifier) const'
/usr/bin/ld: /usr/local/home/jaebaek/sdb/amber.git/out/SWFT/../../third_party/dxc/lib/DxcSupport/HLSLOptions.cpp:407: undefined reference to `llvm::opt::ArgList::hasFlag(llvm::opt::OptSpecifier, llvm::opt::OptSpecifier, bool) const'
/usr/bin/ld: /usr/local/home/jaebaek/sdb/amber.git/out/SWFT/../../third_party/dxc/lib/DxcSupport/HLSLOptions.cpp:410: undefined reference to `llvm::opt::ArgList::getLastArg(llvm::opt::OptSpecifier) const'
/usr/bin/ld: /usr/local/home/jaebaek/sdb/amber.git/out/SWFT/../../third_party/dxc/lib/DxcSupport/HLSLOptions.cpp:416: undefined reference to `llvm::opt::ArgList::hasFlag(llvm::opt::OptSpecifier, llvm::opt::OptSpecifier, bool) const'
/usr/bin/ld: /usr/local/home/jaebaek/sdb/amber.git/out/SWFT/../../third_party/dxc/lib/DxcSupport/HLSLOptions.cpp:417: undefined reference to `llvm::opt::ArgList::getLastArgValue(llvm::opt::OptSpecifier, llvm::StringRef) const'
/usr/bin/ld: /usr/local/home/jaebaek/sdb/amber.git/out/SWFT/../../third_party/dxc/lib/DxcSupport/HLSLOptions.cpp:457: undefined reference to `llvm::opt::ArgList::getLastArgValue(llvm::opt::OptSpecifier, llvm::StringRef) const'
/usr/bin/ld: /usr/local/home/jaebaek/sdb/amber.git/out/SWFT/../../third_party/dxc/lib/DxcSupport/HLSLOptions.cpp:458: undefined reference to `llvm::opt::ArgList::getLastArgValue(llvm::opt::OptSpecifier, llvm::StringRef) const'
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