Target JVM 1.8 for Kotlin

Signed-off-by: Ryan Nett <[email protected]>

Author: rnett

Diff for: tensorflow-core-kotlin/pom.xml

@@ -45,6 +45,8 @@
 
   <properties>
     <kotlin.version>1.4.20</kotlin.version>
+    <kotlin.jvmTarget>1.8</kotlin.jvmTarget>
+
     <native.classifier>${javacpp.platform}${javacpp.platform.extension}</native.classifier>
     <javacpp.platform.extension></javacpp.platform.extension>
     <javacpp.platform.properties>${javacpp.platform}</javacpp.platform.properties>

Diff for: tensorflow-core-kotlin/tensorflow-core-kotlin-api/pom.xml

@@ -127,6 +127,7 @@
             <arg>-Xopt-in=kotlin.contracts.ExperimentalContracts</arg>
             <arg>-Xexplicit-api=strict</arg>
           </args>
+          <jvmTarget>${kotlin.jvmTarget}</jvmTarget>
         </configuration>
 
         <executions>

Diff for: tensorflow-core-kotlin/tensorflow-core-kotlin-generator/pom.xml

@@ -50,6 +50,9 @@
         <groupId>org.jetbrains.kotlin</groupId>
         <artifactId>kotlin-maven-plugin</artifactId>
         <version>${kotlin.version}</version>
+        <configuration>
+          <jvmTarget>${kotlin.jvmTarget}</jvmTarget>
+        </configuration>
 
         <executions>
           <execution>
@@ -73,8 +76,8 @@
         <version>3.5.1</version>
         <configuration>
           <proc>none</proc>
-          <source>1.6</source>
-          <target>1.6</target>
+          <source>1.8</source>
+          <target>1.8</target>
         </configuration>
         <executions>
           <!-- Replacing default-compile as it is treated specially by maven -->