Revert "Upgrade to Kotlin 1.7, add -Xskip-metadata-version-check to buildSrc"

This reverts commit d24230099a.

build.gradle

@@ -40,10 +40,10 @@ def multiplatformModules = [
 def doNotPublish = ["openrndr-demos"]
 
 project.ext {
-    kotlinApiVersion = '1.7'
-    kotlinLanguageVersion = '1.7'
-    kotlinVersion = '1.7.0'
-    kotlinxCoroutinesVersion = '1.6.1'
+    kotlinApiVersion = '1.6'
+    kotlinLanguageVersion = '1.6'
+    kotlinVersion = '1.6.20'
+    kotlinxCoroutinesVersion = '1.6.0'
     kotlinLoggingVersion = '2.1.21'
     kotlinxSerializationVersion = '1.3.2'
     spekVersion = '2.0.15'
@@ -66,8 +66,8 @@ def openrndrUseSnapshot = isReleaseVersion
 project.ext {
     openrndrVersion = ((findProperty("OPENRNDR.version")?:System.getenv("OPENRNDR_VERSION")) ?.replace("v","")) ?: "0.5.1-SNAPSHOT"
     jvmTarget = "1.8"
-    kotlinVersion = "1.7.0"
-    kotlinApiVersion = "1.7"
+    kotlinVersion = "1.6.20"
+    kotlinApiVersion = "1.6"
     spekVersion = "2.0.15"
     libfreenectVersion = "0.5.7-1.5.7"
     librealsense2Version = "2.50.0-1.5.7"

buildSrc/build.gradle.kts

@@ -30,11 +30,4 @@ dependencies {
     preloadImplementation("org.openrndr:openrndr-extensions:$openrndrVersion")
 }
 
-tasks.getByName("compileKotlin").dependsOn("compilePreloadKotlin")
-
-// Here we deal with Gradle 7.4.2 using Kotlin 1.5 while OPENRNDR is compiled using Kotlin 1.7
-// This seems to work at this point in time but may cause serious problems in future scenarios in which either Kotlin,
-// Gradle or OPENRNDR are upgraded.
-tasks.withType<org.jetbrains.kotlin.gradle.tasks.KotlinCompile> {
-    kotlinOptions.freeCompilerArgs = listOf("-Xskip-metadata-version-check")
-}
+tasks.getByName("compileKotlin").dependsOn("compilePreloadKotlin")