Update pinned clang to clang-14

[greg7mdp]

I tried upgrading the clang version we use to build to 14.0 (to match the default in Ubuntu 22.04).

After jumping over some hurdles, I had the following errors when building leap:

/leap/libraries/chain/webassembly/runtimes/eos-vm-oc/LLVMJIT.cpp:24:10: fatal error: 'llvm/ExecutionEngine/Orc/LambdaResolver.h' file not found
#include "llvm/ExecutionEngine/Orc/LambdaResolver.h"
         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In file included from /leap/libraries/chain/webassembly/runtimes/eos-vm-oc/LLVMEmitIR.cpp:43:
/leap/deps/clang-14.0.0/include/llvm/Transforms/InstCombine/InstCombine.h:42:41: error: base class has incomplete type
class InstructionCombiningPass : public FunctionPass {
                                 ~~~~~~~^~~~~~~~~~~~
/leap/deps/clang-14.0.0/include/llvm/Analysis/Passes.h:18:9: note: forward declaration of 'llvm::FunctionPass'
  class FunctionPass;
        ^
In file included from /leap/libraries/chain/webassembly/runtimes/eos-vm-oc/LLVMEmitIR.cpp:43:
/leap/deps/clang-14.0.0/include/llvm/Transforms/InstCombine/InstCombine.h:52:25: error: unknown type name 'AnalysisUsage'
  void getAnalysisUsage(AnalysisUsage &AU) const override;
                        ^
...