Apply LLVM patches for deterministic operand order and correct peephole optimization for minsize (#500)

## Description

Applies LLVM patches that have not been backported to the major version
used in our submodule:

* [LLVM PR #163679](https://github.com/llvm/llvm-project/pull/163679)
  * *"[RISCV] Allow large div peephole optimization for minsize"*
* Fixes peephole optimization of large integers when `minsize` function
attribute is set.
* (Our revive codebase used a workaround that can be removed once this
500 PR is merged and we publish a new LLVM release.)
* [LLVM PR #190219](https://github.com/llvm/llvm-project/pull/190219)
* *"[TargetLowering] Speculative fix for a non-determinism issue between
different compilers"*
* Operand ordering of `mul i256` were different depending on the target
ABI when building LLVM, producing different RISC-V and PVM bytecode for
our Windows vs macOS/linux builds.
* The bytecode divergence (yet functionally equivalent) affected
Solidity contracts containing a value [multiplied by
itself](https://github.com/llvm/llvm-project/issues/190148) (e.g. via
explicit squaring or exponentiation), manifesting primarily when using
optimization level `-O0`.

crates/llvm-builder/src/llvm_path.rs

@@ -20,6 +20,9 @@ impl LLVMPath {
     /// The Emscripten SDK source directory.
     pub const DIRECTORY_EMSDK_SOURCE: &'static str = "./emsdk/";
 
+    /// The directory containing patches to apply to the LLVM source.
+    pub const DIRECTORY_PATCHES: &'static str = "./patches/llvm/";
+
     /// Returns the path to the `llvm` stage 1 host LLVM source module directory.
     pub fn llvm_host_module_llvm() -> anyhow::Result<PathBuf> {
         let mut path = PathBuf::from(Self::DIRECTORY_LLVM_HOST_SOURCE);