Try changing android min-sdk to 21 because :grpc-android-interop-testing:mergeDexDebug task is failing with

> Could not resolve all files for configuration ':grpc-android-interop-testing:debugRuntimeClasspath'.
   > Failed to transform annotation-jvm-1.9.1.jar (androidx.annotation:annotation-jvm:1.9.1) to match attributes {artifactType=android-dex, asm-transformed-variant=NONE, dexing-enable-desugaring=true, dexing-enable-jacoco-instrumentation=false, dexing-is-debuggable=true, dexing-min-sdk=20, org.gradle.category=library, org.gradle.jvm.environment=standard-jvm, org.gradle.libraryelements=jar, org.gradle.status=release, org.gradle.usage=java-runtime, org.jetbrains.kotlin.platform.type=jvm}.
      > Execution failed for DexingWithClasspathTransform: /root/.gradle/caches/modules-2/files-2.1/androidx.annotation/annotation-jvm/1.9.1/b17951747e38bf3986a24431b9ba0d039958aa5f/annotation-jvm-1.9.1.jar.
         > Error while dexing.
   > Failed to transform kotlin-stdlib-1.9.24.jar (org.jetbrains.kotlin:kotlin-stdlib:1.9.24) to match attributes {artifactType=android-dex, asm-transformed-variant=NONE, dexing-enable-desugaring=true, dexing-enable-jacoco-instrumentation=false, dexing-is-debuggable=true, dexing-min-sdk=20, org.gradle.category=library, org.gradle.libraryelements=jar, org.gradle.status=release, org.gradle.usage=java-runtime}.
      > Execution failed for DexingWithClasspathTransform: /root/.gradle/caches/modules-2/files-2.1/org.jetbrains.kotlin/kotlin-stdlib/1.9.24/9928532f12c66ad816a625b3f9984f8368ca6d2b/kotlin-stdlib-1.9.24.jar.
         > Error while dexing.

Author: kannanjgithub

android-interop-testing/build.gradle

@@ -33,10 +33,6 @@ android {
 
     defaultConfig {
         applicationId "io.grpc.android.integrationtest"
-        // Held back to 20 as Gradle fails to build at the 21 level. This is
-        // presumably a Gradle bug that can be revisited later.
-        // Maybe this issue: https://github.com/gradle/gradle/issues/20778
-        minSdkVersion 20
         targetSdkVersion 33
         versionCode 1
         versionName "1.0"