[clang] [HIP] Use complete toolchain in --offload-device-only (PR #205243)

[Matt Arsenault via cfe-commits]

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@@ -302,6 +302,15 @@ Tool *HIPAMDToolChain::buildLinker() const {
   return new tools::AMDGCN::Linker(*this);
 }
 
+LTOKind HIPAMDToolChain::getLTOMode(const ArgList &Args,
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arsenm wrote:

Shouldn't put anything in HIPAMDToolChain, I am trying to remove it in #204863

https://github.com/llvm/llvm-project/pull/205243