CocoaPods: Detect the real path to Gradle wrapper.

Previously the CocoaPods plugin assumed that Gradle wrapper
is located in the project directory. But the project may be
a part of multiproject build and wrapper may be located in
the root directory of such a build. Also the build may not
have the wrapper at all.

This patch looks for the wrapper in the root directory of the
build and runs the local Gradle if there is no wrapper.

libraries/tools/kotlin-gradle-plugin/src/main/kotlin/org/jetbrains/kotlin/gradle/tasks/CocoapodsTasks.kt

@@ -7,6 +7,7 @@ package org.jetbrains.kotlin.gradle.tasks
 
 import org.gradle.api.DefaultTask
 import org.gradle.api.tasks.*
+import org.gradle.api.tasks.wrapper.Wrapper
 import org.jetbrains.kotlin.gradle.plugin.cocoapods.CocoapodsExtension
 import org.jetbrains.kotlin.gradle.plugin.cocoapods.KotlinCocoapodsPlugin
 import org.jetbrains.kotlin.gradle.plugin.cocoapods.KotlinCocoapodsPlugin.Companion.KOTLIN_TARGET_FOR_DEVICE
@@ -38,6 +39,14 @@ open class PodspecTask : DefaultTask() {
             "|    spec.dependency '${pod.name}'$versionSuffix"
         }.joinToString(separator = "\n")
 
+        // Try to construct a path to Gradle wrapper. If there is no wrapper, just run the local Gradle.
+        val gradleWrapper = (project.rootProject.tasks.getByName("wrapper") as? Wrapper)?.scriptFile
+        val gradleCommand = if (gradleWrapper != null && gradleWrapper.exists()) {
+            "\$REPO_ROOT/${gradleWrapper.toRelativeString(project.projectDir)}"
+        } else {
+            "gradle"
+        }
+
         outputFile.writeText("""
             |Pod::Spec.new do |spec|
             |    spec.name                     = '$specName'
@@ -69,7 +78,7 @@ open class PodspecTask : DefaultTask() {
             |            :script => <<-SCRIPT
             |                set -ev
             |                REPO_ROOT="${'$'}PODS_TARGET_SRCROOT"
-            |                ${'$'}REPO_ROOT/gradlew -p "${'$'}REPO_ROOT" syncFramework \
+            |                "$gradleCommand" -p "${'$'}REPO_ROOT" syncFramework \
             |                    -P${KotlinCocoapodsPlugin.TARGET_PROPERTY}=${'$'}KOTLIN_TARGET \
             |                    -P${KotlinCocoapodsPlugin.CONFIGURATION_PROPERTY}=${'$'}CONFIGURATION \
             |                    -P${KotlinCocoapodsPlugin.CFLAGS_PROPERTY}="${'$'}OTHER_CFLAGS" \