Building rust with LLVM Fork - rust

Question

Following the instructions here, I have tried building rust with a fork of LLVM which has a back-end for a new target.
I have:
Recursively cloned the Rust repository
Edited config.toml to add the new target,
Replaced with custom LLVM Fork by:
cd src/llvm-project
git remote add custom-fork [link to custom fork]
git checkout custom-fork/branch
then committing these changes.
Build rust with x.py build.
The LLVM fork has been rebased onto LLVM 13.0
cargo:warning=llvm-wrapper/PassWrapper.cpp: In function ‘void LLVMRustPrintTargetCPUs(LLVMTargetMachineRef)’:
cargo:warning=llvm-wrapper/PassWrapper.cpp:502:57: error: ‘const class llvm::MCSubtargetInfo’ has no member named ‘getCPUTable’
cargo:warning= 502 | const ArrayRef<SubtargetSubTypeKV> CPUTable = MCInfo->getCPUTable();
cargo:warning= | ^~~~~~~~~~~
cargo:warning=llvm-wrapper/PassWrapper.cpp: In function ‘size_t LLVMRustGetTargetFeaturesCount(LLVMTargetMachineRef)’:
cargo:warning=llvm-wrapper/PassWrapper.cpp:519:58: error: ‘const class llvm::MCSubtargetInfo’ has no member named ‘getFeatureTable’; did you mean ‘getFeatureBits’?
cargo:warning= 519 | const ArrayRef<SubtargetFeatureKV> FeatTable = MCInfo->getFeatureTable();
cargo:warning= | ^~~~~~~~~~~~~~~
cargo:warning= | getFeatureBits
cargo:warning=llvm-wrapper/PassWrapper.cpp: In function ‘void LLVMRustGetTargetFeature(LLVMTargetMachineRef, size_t, const char**, const char**)’:
cargo:warning=llvm-wrapper/PassWrapper.cpp:527:58: error: ‘const class llvm::MCSubtargetInfo’ has no member named ‘getFeatureTable’; did you mean ‘getFeatureBits’?
cargo:warning= 527 | const ArrayRef<SubtargetFeatureKV> FeatTable = MCInfo->getFeatureTable();
cargo:warning= | ^~~~~~~~~~~~~~~
cargo:warning= | getFeatureBits
exit status: 1
--- stderr
This same error occurs when using the upstream LLVM; I'm unsure whether this is due to a patch that has been applied to the rust LLVM fork that needs to be ported over, or if I just need to change something in the llvm-wrapper.