[#78] Fix build on Apple Silicon

build-conventions/src/main/kotlin/zcash.kotlin-multiplatform-build-conventions.gradle.kts

@@ -3,11 +3,23 @@ import org.gradle.jvm.toolchain.JavaToolchainSpec
 pluginManager.withPlugin("org.jetbrains.kotlin.multiplatform") {
     extensions.findByType<org.jetbrains.kotlin.gradle.dsl.KotlinMultiplatformExtension>()?.apply {
         jvmToolchain {
-            val javaVersion = JavaVersion.toVersion(project.property("ANDROID_JVM_TARGET").toString())
+            val javaVersion = JavaVersion.toVersion(project.property("JVM_TOOLCHAIN").toString())
             val javaLanguageVersion = JavaLanguageVersion.of(javaVersion.majorVersion)
             (this as JavaToolchainSpec).languageVersion.set(javaLanguageVersion)
         }
 
+        targets.matching { it.platformType.name == "jvm" }.all {
+            (this as org.jetbrains.kotlin.gradle.targets.jvm.KotlinJvmTarget).apply {
+                val javaTargetVersion = project.property("ANDROID_JVM_TARGET").toString()
+
+                compilations.all {
+                    kotlinOptions {
+                        jvmTarget = javaTargetVersion
+                    }
+                }
+            }
+        }
+
         targets.all {
             compilations.all {
                 kotlinOptions {

gradle.properties

@@ -72,5 +72,10 @@ KOTLINX_COROUTINES_VERSION=1.5.2
 KOTLIN_VERSION=1.5.31
 ZCASH_SDK_VERSION=1.3.0-beta18
 
+# Toolchain is the Java version used to build the application, which is separate from the
+# Java version used to run the application.  Android requires a minimum of 11.  Apple Silicon
+# requires a newer toolchain.  Kotlin won't support Java 17 until Kotlin 1.6
+JVM_TOOLCHAIN=16
+
 # This shouldn't be changed, as Android doesn't support targets beyond Java 8
 ANDROID_JVM_TARGET=1.8