Fix macOS CI: add homebrew bison to GITHUB_PATH

The system bison (2.3) doesn't support the %code directive.
Add homebrew's bison to GITHUB_PATH so it persists across all steps.

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

Author: greggdonovan

.github/workflows/build.yml

@@ -86,14 +86,13 @@ jobs:
       - name: Install dependencies
         run: |
           brew install automake bison flex boost libevent openssl libtool pkg-config
+          echo "$(brew --prefix bison)/bin" >> $GITHUB_PATH
 
       - name: Run bootstrap
         run: ./bootstrap.sh
 
       - name: Run configure
-        run: |
-          export PATH="$(brew --prefix bison)/bin:$PATH"
-          ./configure --disable-debug --disable-tests --disable-libs
+        run: ./configure --disable-debug --disable-tests --disable-libs
 
       - name: Run make
         run: make -j$(sysctl -n hw.ncpu)
@@ -597,6 +596,7 @@ jobs:
       - name: Install dependencies
         run: |
           brew install automake bison flex boost libevent openssl libtool pkg-config
+          echo "$(brew --prefix bison)/bin" >> $GITHUB_PATH
 
       - name: Set up Python
         uses: actions/setup-python@v6
@@ -613,9 +613,7 @@ jobs:
         run: ./bootstrap.sh
 
       - name: Run configure
-        run: |
-          export PATH="$(brew --prefix bison)/bin:$PATH"
-          ./configure $(echo $CONFIG_ARGS_FOR_LIBS | sed 's/without-py3/with-py3/')
+        run: ./configure $(echo $CONFIG_ARGS_FOR_LIBS | sed 's/without-py3/with-py3/')
 
       - uses: actions/download-artifact@v6
         with: