Current README instruction lead to build failure when building mutated LLVM

[JonathanFoo0523]

The current README instructions, even after addressing the absolute path issue in the Dredd script (issue #7) and ensuring that the LLVM version described in the README is used to build Dredd and LLVM, still result in the following compilation errors:

/home/ubuntu/llvm-17.0.4-mutant-tracking/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp:1616:341: error: reference to local binding 'ICmp' declared in enclosing function 'llvm::InstCombinerImpl::foldAllocaCmp'

A minimal reproducible example of this error can be shown by applying dredd to

#include <tuple>
int bar();


int foo(bool isAnd) {
    auto [someInt, someMask] = std::pair<int, int>(1, 2);
    unsigned CombinedMask = someMask & bar();
    return 0;
}

which introduces a lambda of the form:

[&]() -> { ... someMask ...}

and causes

error: reference to local binding 'someMask' declared in enclosing function 'foo`

when compiling with clang-15, which is explicitly stated in the README instruction.

[JonathanFoo0523]

I will implement a workaround by specifying both build to make use of compiler in dredd/third-party/clang+llvm/bin, instead of clang-15