Add 'export CPPFLAGS' line to macOS build

.github/workflows/build-macos-package.yml

@@ -17,12 +17,6 @@ jobs:
     steps:
     - uses: actions/checkout@v2
 
-    # just to see output
-    - run: echo $JAVA_HOME
-    - run: echo $JAVA_INCLUDE_DIR
-    - run: export JAVA_INCLUDE_DIR=/usr/local/Cellar/openjdk/15.0.1/include
-    - run: brew reinstall openjdk
-
     - name: Setup Haskell
       uses: actions/setup-haskell@v1
       id: setup-haskell-cabal
@@ -38,6 +32,7 @@ jobs:
 
     - name: Build macOS package
       run: |
+        export CPPFLAGS="-I/usr/local/opt/openjdk/include"
         make pkg
 
     - name: Upload artifact