Update build instructions

Builds should always be done using the Gradle wrapper to avoid version
issues, and the deploy task no longer exists (the standard Gradle
assemble task should be used instead).

README.md

@@ -27,8 +27,8 @@ This derived work is, like SableCC, covered by the GNU Lesser General Public Lic
 Building
 ---
 
-* Clone the repository
-* Run the deploy target using gradle. If you don't have gradle installed, you can use the gradlew wrapper scripts, e.g., under Linux use './gradlew deploy'
+* Clone the repository.
+* Run the `assemble` target using Gradle (`./gradlew assemble` on Linux/macOS/etc., `gradlew.bat assemble` on Windows).
 * The binary is located in the build/libs subdirectory.
 
 Documentation