chore: Add notes about common build problems in registry readme

registry/contract/README.md

@@ -38,3 +38,43 @@ Add multisig deployment administration for Data team and SREs (DAO?).
 ./build.sh
 near deploy --wasmFile ./target/wasm32-unknown-unknown/release/registry.wasm --accountId registry.queryapi.testnet
 ```
+
+## Issues encountered while building
+
+### Clang
+
+The default version of `clang` on MacOS cannot build `wasm32-unknown-unknown`, therefore another version must be installed:
+```sh
+brew install llvm
+```
+and can be used via setting the `CC` environment variable:
+```sh
+CC="/opt/homebrew/Cellar/llvm/17.0.6/bin/clang" cargo build --target wasm32-unknown-unknown
+```
+
+### near-primitives usize
+The `near-primitives` crate internally hard-codes `usize` as 8bits, this becomes a problem when targetting 32bit architecture (wasm32), which expects a `usize` of 4bits. To Bypass this issue the following patch can be applied to the local version of the crate in `~/.cargo/registry/src/index.crates.io-6f17d22bba15001f/near-primitives-0.17.0/src/rand.rs`:
+```patch
+diff --git a/core/primitives/src/rand.rs b/core/primitives/src/rand.rs
+index a79c8fd1b..17978a199 100644
+--- a/core/primitives/src/rand.rs
++++ b/core/primitives/src/rand.rs
+@@ -57,16 +57,7 @@ impl WeightedIndex {
+     }
+
+     pub fn sample(&self, seed: [u8; 32]) -> usize {
+-        let usize_seed = Self::copy_8_bytes(&seed[0..8]);
+-        let balance_seed = Self::copy_16_bytes(&seed[8..24]);
+-        let uniform_index = usize::from_le_bytes(usize_seed) % self.aliases.len();
+-        let uniform_weight = Balance::from_le_bytes(balance_seed) % self.weight_sum;
+-
+-        if uniform_weight < self.no_alias_odds[uniform_index] {
+-            uniform_index
+-        } else {
+-            self.aliases[uniform_index] as usize
+-        }
++        0
+     }
+
+     pub fn get_aliases(&self) -> &[u64] {
+```