Update build.yml

.github/workflows/build.yml

@@ -189,8 +189,6 @@ jobs:
             echo "PYTHON=${PYTHON_INSTALL_PATH}\python.exe" >> $GITHUB_ENV
             echo "GAM_ARCHIVE_ARCH=${GAM_ARCHIVE_ARCH}" >> $GITHUB_ENV
             echo "WIX_ARCH=${WIX_ARCH}" >> $GITHUB_ENV
-            # supposed to tell VS nmake to do parallel build
-            echo "CL=/MP" >> $GITHUB_ENV
           fi
           echo "We'll run make with: ${MAKEOPT}"
           echo "JID=${jid}" >> $GITHUB_ENV
@@ -247,6 +245,9 @@ jobs:
       - name: Make OpenSSL
         if: matrix.goal == 'build' && steps.cache-python-ssl.outputs.cache-hit != 'true'
         run: |
+          if [[ "${RUNNER_OS}" == "Windows" ]]; then
+            export CL="/MP"
+          fi
           for openssl_arch in $openssl_archs; do
             cd "${GITHUB_WORKSPACE}/src/openssl-${openssl_arch}"
             $MAKE "${MAKEOPT}"