Upgrade the kotlinx-serialization version

* This fixes the incompatibility with the newer serialization
  versions.
* watchosX64 target can now be added.

Fixes #118

Author: dkhalanskyjb

core/build.gradle.kts

@@ -36,6 +36,7 @@ kotlin {
             target("watchosArm32")
             target("watchosArm64")
             target("watchosX86")
+            target("watchosX64")
             target("tvosArm64")
             target("tvosX64")
         }

gradle.properties

@@ -4,7 +4,7 @@ group=org.jetbrains.kotlinx
 version=0.2.0
 versionSuffix=SNAPSHOT
 
-serializationVersion=1.1.0
+serializationVersion=1.2.1
 
 kotlin.mpp.enableGranularSourceSetsMetadata=true
 kotlin.mpp.enableCompatibilityMetadataVariant=true

serialization/build.gradle.kts

@@ -19,6 +19,7 @@ kotlin {
         target("watchosArm32")
         target("watchosArm64")
         target("watchosX86")
+        target("watchosX64")
         target("tvosArm64")
         target("tvosX64")
     }