Consolidate some constants and add kotlin target JVM version.

microbenchmark/build.gradle.kts

@@ -4,15 +4,15 @@ plugins {
   id("com.android.library")
   id("androidx.benchmark")
   id("org.jetbrains.kotlin.android")
-  id("android-constants")
   id("ktlint")
 }
 
-val signalBuildToolsVersion: String by extra
-val signalCompileSdkVersion: String by extra
-val signalTargetSdkVersion: Int by extra
-val signalMinSdkVersion: Int by extra
-val signalJavaVersion: JavaVersion by extra
+val signalBuildToolsVersion: String by rootProject.extra
+val signalCompileSdkVersion: String by rootProject.extra
+val signalTargetSdkVersion: Int by rootProject.extra
+val signalMinSdkVersion: Int by rootProject.extra
+val signalJavaVersion: JavaVersion by rootProject.extra
+val signalKotlinJvmTarget: String by rootProject.extra
 
 android {
   namespace = "org.signal.microbenchmark"
@@ -24,7 +24,7 @@ android {
   }
 
   kotlinOptions {
-    jvmTarget = "11"
+    jvmTarget = signalKotlinJvmTarget
   }
 
   defaultConfig {