CI: Use Android platform-21 (#1668)

Assuming platform-21 corresponds to Android API Level 21.
We have this statement in the README and we have this setup
in further CI pipelines. It is better to catch non supported
calls before merging

Relates-To: MINOR

Signed-off-by: Rustam Gamidov <ext-rustam.gamidov@here.com>

Author: rustam-gamidov-here

scripts/android/build.sh

@@ -1,6 +1,6 @@
 #!/bin/bash -ex
 #
-# Copyright (C) 2019-2024 HERE Europe B.V.
+# Copyright (C) 2019-2026 HERE Europe B.V.
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
 # you may not use this file except in compliance with the License.
@@ -19,15 +19,15 @@
 
 #
 # This script will compile Data SDK for C++
-# with ANDROID_PLATFORM=android-28 and -DANDROID_ABI=arm64-v8a
+# with ANDROID_PLATFORM=android-21 and -DANDROID_ABI=arm64-v8a
 # by using Android NDK 21.
 #
 
 # Install required NDK version (output disabled as it causes issues during page loading)
 env
 ${ANDROID_SDK_ROOT}/cmdline-tools/latest/bin/sdkmanager --list
 ${ANDROID_SDK_ROOT}/cmdline-tools/latest/bin/sdkmanager --install "ndk;21.3.6528147" --sdk_root=${ANDROID_HOME} >/dev/null
-${ANDROID_SDK_ROOT}/cmdline-tools/latest/bin/sdkmanager --install "platforms;android-28" >/dev/null
+${ANDROID_SDK_ROOT}/cmdline-tools/latest/bin/sdkmanager --install "platforms;android-21" >/dev/null
 ${ANDROID_SDK_ROOT}/cmdline-tools/latest/bin/sdkmanager --list
 export ANDROID_NDK_HOME=$ANDROID_HOME/ndk/21.3.6528147
 env
@@ -38,7 +38,7 @@ ls -la $ANDROID_NDK_HOME/platforms
 mkdir -p build && cd build
 cmake .. -DCMAKE_TOOLCHAIN_FILE="$ANDROID_HOME/ndk/21.3.6528147/build/cmake/android.toolchain.cmake" \
   -DCMAKE_BUILD_TYPE=RelWithDebInfo \
-  -DANDROID_PLATFORM=android-28 \
+  -DANDROID_PLATFORM=android-21 \
   -DANDROID_ABI=arm64-v8a \
   -DANDROID_NDK="$ANDROID_HOME/ndk/21.3.6528147" \
   -DOLP_SDK_ENABLE_TESTING=NO \