[SymForce-External] CI Updates

- Fix wheel build on macos (credit to @Djolo1802)
- Clang 15

Topic: sfci-misc
Closes symforce-org#372
GitOrigin-RevId: db3cd01247bf0e4868b8c1d6dc7fe3b2c374a162

.github/scripts/mac_install_gmp.sh

@@ -10,8 +10,8 @@ set -ex
 if [ "$CIBW_ARCHS_MACOS" = "arm64" ]; then
   mkdir arm-homebrew
   curl -L https://github.com/Homebrew/brew/tarball/master | tar xz --strip 1 -C arm-homebrew
-  response=$(./arm-homebrew/bin/brew fetch --force --bottle-tag=arm64_big_sur gmp | grep "Downloaded to: " | cut -c 16-)
-  echo $response
-  # parsed=($response)
-  ./arm-homebrew/bin/brew install $response
+  cache_path=$(./arm-homebrew/bin/brew --cache gmp)
+  echo "Using cache_path: ${cache_path}"
+  curl --output ${cache_path} https://symforce.org/downloads/gmp-6.2.1_1.arm64_big_sur.bottle.tar.gz
+  ./arm-homebrew/bin/brew install ${cache_path}
 fi

.github/workflows/ci.yml

@@ -41,13 +41,13 @@ jobs:
               CXX: clang++-7
               package: clang-7
               repos: []
-          # Clang 14
+          # Clang 15
           - os: ubuntu-22.04
             python: python3.10
             compiler:
-              C: clang-14
-              CXX: clang++-14
-              package: clang-14
+              C: clang-15
+              CXX: clang++-15
+              package: clang-15
               repos: []
     steps:
       - name: Checkout