add BIP341 to the threshold Schnorr rust example (#1071)

Author: altkdf

.github/workflows/rust-threshold-schnorr-example.yml

@@ -20,7 +20,9 @@ jobs:
     steps:
       - uses: actions/checkout@v1
       - name: Provision Darwin
-        run: bash .github/workflows/provision-darwin.sh
+        run: |
+          bash .github/workflows/provision-darwin.sh
+          brew install llvm
       - name: Provision PocketIC
         run: bash .github/workflows/provision-pocket-ic-server.sh
       - name: Rust Threshold Schnorr Darwin