Use gradle instead of gradlew in build workflow

Replaces the use of the Gradle wrapper (gradlew) with the system-installed gradle command in the GitHub Actions build workflow.

Author: DaCodeChick

.github/workflows/build.yml

@@ -31,7 +31,7 @@ jobs:
         echo "GHIDRA_INSTALL_DIR=$GHIDRA_DIR" >> $GITHUB_ENV
         
     - name: Build with Gradle
-      run: ./gradlew build -PGHIDRA_INSTALL_DIR=$GHIDRA_INSTALL_DIR
+      run: ./gradle build -PGHIDRA_INSTALL_DIR=$GHIDRA_INSTALL_DIR
 
     - name: Upload build artifacts
       uses: actions/upload-artifact@v4