Cleanup some Kotlin warnings in build.gradle.kts files (#8137)

---

- [x] I’ve reviewed the contributor guide and applied the relevant
portions to this PR.

Author: jwren

build.gradle.kts

@@ -60,12 +60,16 @@ println("javaVersion: $javaVersion")
 println("group: $group")
 
 var jvmVersion: JvmTarget
-if (javaVersion == "17") {
-  jvmVersion = JvmTarget.JVM_17
-} else if (javaVersion == "21") {
-  jvmVersion = JvmTarget.JVM_21
-} else {
-  throw IllegalArgumentException("javaVersion must be defined in the product matrix as either \"17\" or \"21\", but is not for $ideaVersion")
+jvmVersion = when (javaVersion) {
+  "17" -> {
+    JvmTarget.JVM_17
+  }
+  "21" -> {
+    JvmTarget.JVM_21
+  }
+  else -> {
+    throw IllegalArgumentException("javaVersion must be defined in the product matrix as either \"17\" or \"21\", but is not for $ideaVersion")
+  }
 }
 kotlin {
   compilerOptions {
@@ -75,12 +79,18 @@ kotlin {
 }
 
 var javaCompatibilityVersion: JavaVersion
-if (javaVersion == "17") {
-  javaCompatibilityVersion = JavaVersion.VERSION_17
-} else if (javaVersion == "21") {
-  javaCompatibilityVersion = JavaVersion.VERSION_21
-} else {
-  throw IllegalArgumentException("javaVersion must be defined in the product matrix as either \"17\" or \"21\", but is not for $ideaVersion")
+javaCompatibilityVersion = when (javaVersion) {
+  "17" -> {
+    JavaVersion.VERSION_17
+  }
+
+  "21" -> {
+    JavaVersion.VERSION_21
+  }
+
+  else -> {
+    throw IllegalArgumentException("javaVersion must be defined in the product matrix as either \"17\" or \"21\", but is not for $ideaVersion")
+  }
 }
 java {
   sourceCompatibility = javaCompatibilityVersion

flutter-idea/build.gradle.kts

@@ -7,7 +7,6 @@
 import org.gradle.api.tasks.testing.logging.TestExceptionFormat
 import org.jetbrains.intellij.platform.gradle.IntelliJPlatformType
 import org.jetbrains.intellij.platform.gradle.TestFrameworkType
-import org.jetbrains.intellij.platform.gradle.models.ProductRelease
 import org.jetbrains.intellij.platform.gradle.tasks.VerifyPluginTask
 import org.jetbrains.kotlin.gradle.dsl.JvmTarget
 import org.jetbrains.kotlin.gradle.dsl.KotlinVersion
@@ -40,12 +39,16 @@ val javaVersion = providers.gradleProperty("javaVersion").get()
 group = "io.flutter"
 
 var jvmVersion: JvmTarget
-if (javaVersion == "17") {
-  jvmVersion = JvmTarget.JVM_17
-} else if (javaVersion == "21") {
-  jvmVersion = JvmTarget.JVM_21
-} else {
-  throw IllegalArgumentException("javaVersion must be defined in the product matrix as either \"17\" or \"21\", but is not for $ideaVersion")
+jvmVersion = when (javaVersion) {
+  "17" -> {
+    JvmTarget.JVM_17
+  }
+  "21" -> {
+    JvmTarget.JVM_21
+  }
+  else -> {
+    throw IllegalArgumentException("javaVersion must be defined in the product matrix as either \"17\" or \"21\", but is not for $ideaVersion")
+  }
 }
 kotlin {
   compilerOptions {
@@ -55,12 +58,16 @@ kotlin {
 }
 
 var javaCompatibilityVersion: JavaVersion
-if (javaVersion == "17") {
-  javaCompatibilityVersion = JavaVersion.VERSION_17
-} else if (javaVersion == "21") {
-  javaCompatibilityVersion = JavaVersion.VERSION_21
-} else {
-  throw IllegalArgumentException("javaVersion must be defined in the product matrix as either \"17\" or \"21\", but is not for $ideaVersion")
+javaCompatibilityVersion = when (javaVersion) {
+  "17" -> {
+    JavaVersion.VERSION_17
+  }
+  "21" -> {
+    JavaVersion.VERSION_21
+  }
+  else -> {
+    throw IllegalArgumentException("javaVersion must be defined in the product matrix as either \"17\" or \"21\", but is not for $ideaVersion")
+  }
 }
 java {
   sourceCompatibility = javaCompatibilityVersion

flutter-studio/build.gradle.kts

@@ -4,7 +4,6 @@
  * found in the LICENSE file.
  */
 
-import org.jetbrains.intellij.platform.gradle.IntelliJPlatformType
 import org.jetbrains.intellij.platform.gradle.TestFrameworkType
 import org.jetbrains.kotlin.gradle.dsl.JvmTarget
 import org.jetbrains.kotlin.gradle.dsl.KotlinVersion
@@ -40,12 +39,16 @@ val javaVersion = providers.gradleProperty("javaVersion").get()
 group = "io.flutter"
 
 var jvmVersion: JvmTarget
-if (javaVersion == "17") {
-  jvmVersion = JvmTarget.JVM_17
-} else if (javaVersion == "21") {
-  jvmVersion = JvmTarget.JVM_21
-} else {
-  throw IllegalArgumentException("javaVersion must be defined in the product matrix as either \"17\" or \"21\", but is not for $ideaVersion")
+jvmVersion = when (javaVersion) {
+  "17" -> {
+    JvmTarget.JVM_17
+  }
+  "21" -> {
+    JvmTarget.JVM_21
+  }
+  else -> {
+    throw IllegalArgumentException("javaVersion must be defined in the product matrix as either \"17\" or \"21\", but is not for $ideaVersion")
+  }
 }
 kotlin {
   compilerOptions {
@@ -55,12 +58,16 @@ kotlin {
 }
 
 var javaCompatibilityVersion: JavaVersion
-if (javaVersion == "17") {
-  javaCompatibilityVersion = JavaVersion.VERSION_17
-} else if (javaVersion == "21") {
-  javaCompatibilityVersion = JavaVersion.VERSION_21
-} else {
-  throw IllegalArgumentException("javaVersion must be defined in the product matrix as either \"17\" or \"21\", but is not for $ideaVersion")
+javaCompatibilityVersion = when (javaVersion) {
+  "17" -> {
+    JavaVersion.VERSION_17
+  }
+  "21" -> {
+    JavaVersion.VERSION_21
+  }
+  else -> {
+    throw IllegalArgumentException("javaVersion must be defined in the product matrix as either \"17\" or \"21\", but is not for $ideaVersion")
+  }
 }
 java {
   sourceCompatibility = javaCompatibilityVersion