update cmake to 3.20.1

android/build-commissioner-libs.sh

@@ -46,6 +46,12 @@ cd "${CUR_DIR}"
 readonly BUILD_DIR=".build-$ANDROID_ABI"
 
 mkdir -p "$BUILD_DIR" && cd "$BUILD_DIR"
+
+# Sometimes the java binding will not be rebuilt even of commissioner.hpp is updated.
+# This will enforce rebuilding of the java binding in case the commissioner API is changed.
+# Don't need this when https://github.com/openthread/ot-commissioner/pull/262 is merged
+rm -rf src/java
+
 cmake -GNinja \
     -DCMAKE_TOOLCHAIN_FILE="$ANDROID_NDK_HOME"/build/cmake/android.toolchain.cmake \
     -DANDROID_ABI="$ANDROID_ABI" \