Fix GitHub Actions workflow runner issues

- Update Linux workflow to use ubuntu-latest instead of ubuntu-20.04
  (ubuntu-20.04 has limited runner availability causing 24h timeouts)
- Update apt-key to use gpg keyring method (apt-key is deprecated)
- Update Mac workflow to install gcc via homebrew (g++-11 not pre-installed)
- Use dynamic gcc version detection on macOS
- Update checkout actions to v4

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: lums658

.github/workflows/build_cmake.yml

@@ -1,45 +1,40 @@
-# Workflow to configure with cmake and build with gcc-10
+# Workflow to configure with cmake and build with gcc
 
 name: Build with gcc-11
 
 on:
   push:
     branches: [ master, sc_release ]
-  workflow_dispatch: 
-
+  workflow_dispatch:
 
 env:
-  GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }} 
+  GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
 
 jobs:
   build:
 
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-latest
 
     steps:
 
     - name: Checkout NWgr
-      uses: actions/checkout@v2
+      uses: actions/checkout@v4
       with:
         path: NWgr
 
-    - name: prep
+    - name: Install dependencies
       run: |
-        wget https://apt.repos.intel.com/intel-gpg-keys/GPG-PUB-KEY-INTEL-SW-PRODUCTS.PUB      \
-             && sudo apt-key add GPG-PUB-KEY-INTEL-SW-PRODUCTS.PUB                             \
-             && rm GPG-PUB-KEY-INTEL-SW-PRODUCTS.PUB                                           \
-             && sudo add-apt-repository "deb https://apt.repos.intel.com/oneapi all main"      \
-             && sudo apt-get update
-        DEBIAN_FRONTEND=noninteractive \
-            sudo apt-get -y install    \
-            intel-oneapi-tbb-devel
-        sudo add-apt-repository -y ppa:ubuntu-toolchain-r/test
-        DEBIAN_FRONTEND=noninteractive   \
-            sudo apt-get -y install      \
-            gcc-11                       \
-            g++-11
+        # Install Intel oneAPI TBB
+        wget -O- https://apt.repos.intel.com/intel-gpg-keys/GPG-PUB-KEY-INTEL-SW-PRODUCTS.PUB \
+          | gpg --dearmor | sudo tee /usr/share/keyrings/oneapi-archive-keyring.gpg > /dev/null
+        echo "deb [signed-by=/usr/share/keyrings/oneapi-archive-keyring.gpg] https://apt.repos.intel.com/oneapi all main" \
+          | sudo tee /etc/apt/sources.list.d/oneAPI.list
+        sudo apt-get update
+        DEBIAN_FRONTEND=noninteractive sudo apt-get -y install intel-oneapi-tbb-devel
+        # Install gcc-11 (available on ubuntu-22.04+)
+        DEBIAN_FRONTEND=noninteractive sudo apt-get -y install gcc-11 g++-11
         sudo update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-11 90 --slave /usr/bin/g++ g++ /usr/bin/g++-11
-        sudo update-alternatives --install /usr/bin/cc  cc /usr/bin/gcc 30
+        sudo update-alternatives --install /usr/bin/cc cc /usr/bin/gcc 30
         sudo update-alternatives --install /usr/bin/c++ c++ /usr/bin/g++ 30
 
     - name: cmake

.github/workflows/build_cmake_mac.yml

@@ -1,18 +1,18 @@
-# Workflow to configure with cmake and build with gcc-10
+# Workflow to configure with cmake and build with gcc
 
-name: Build with gcc-11 (Mac)
+name: Build with gcc (Mac)
 
 on:
-  push: 
+  push:
     branches: [ master, sc_release ]
-  workflow_dispatch: 
+  workflow_dispatch:
 
 #  pull_request:
 #    branches:
 #      - '*'
 
 env:
-  GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }} 
+  GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
 
 jobs:
   build:
@@ -22,23 +22,27 @@ jobs:
     steps:
 
     - name: Checkout NWgr
-      uses: actions/checkout@v2
+      uses: actions/checkout@v4
       with:
         path: NWgr
 
-# The macos image evidently has gcc-11 and cmake 3.22 pre-installed
-    - name: prep
+    - name: Install dependencies
       run: |
         brew update
-        brew install tbb
+        brew install gcc tbb
 
     - name: cmake
       run: |
         cd NWgr
         mkdir build
         cd build
-        export TBBROOT=/opt/intel/oneapi/tbb/latest
-        cmake .. -DCMAKE_BUILD_TYPE=RelWithDebInfo -DCMAKE_CXX_COMPILER=g++-11 -DNWGRAPH_BUILD_DOCS=OFF -DNWGRAPH_BUILD_TESTS=ON
+        # Find the highest gcc version installed by homebrew
+        GCC_VERSION=$(ls /opt/homebrew/bin/g++-* 2>/dev/null | grep -o '[0-9]*$' | sort -n | tail -1)
+        if [ -z "$GCC_VERSION" ]; then
+          GCC_VERSION=$(ls /usr/local/bin/g++-* 2>/dev/null | grep -o '[0-9]*$' | sort -n | tail -1)
+        fi
+        echo "Using g++-$GCC_VERSION"
+        cmake .. -DCMAKE_BUILD_TYPE=RelWithDebInfo -DCMAKE_CXX_COMPILER=g++-$GCC_VERSION -DNWGRAPH_BUILD_DOCS=OFF -DNWGRAPH_BUILD_TESTS=ON
 
     - name: make
       run: |