[Gradle] Do not try snapshotting non-existent classpath entries

The fix changes only Gradle's side of the transformation to be consistent with general Gradle behaviour for non-existent dependencies in classpath
^KT-62101 In Progress

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/kotlin/org/jetbrains/kotlin/gradle/GeneralClasspathSnapshotIT.kt

@@ -7,7 +7,6 @@ package org.jetbrains.kotlin.gradle
 
 import org.gradle.util.GradleVersion
 import org.jetbrains.kotlin.gradle.testbase.*
-import org.junit.jupiter.api.Disabled
 import org.junit.jupiter.api.DisplayName
 
 @JvmGradlePluginTests
@@ -15,7 +14,6 @@ import org.junit.jupiter.api.DisplayName
 class GeneralClasspathSnapshotIT : KGPBaseTest() {
     override val defaultBuildOptions = super.defaultBuildOptions.copy(useGradleClasspathSnapshot = true) // ensure classpath snapshotting is enabled
 
-    @Disabled
     @DisplayName("Non-existent dependency files do not fail the build")
     @GradleTest
     fun nonExistentDependency(gradleVersion: GradleVersion) {

libraries/tools/kotlin-gradle-plugin/src/common/kotlin/org/jetbrains/kotlin/gradle/internal/transforms/BuildToolsApiClasspathEntrySnapshotTransform.kt

@@ -71,6 +71,8 @@ abstract class BuildToolsApiClasspathEntrySnapshotTransform : TransformAction<Bu
             checkVersionConsistency()
         }
         val classpathEntryInputDirOrJar = inputArtifact.get().asFile
+        if (!classpathEntryInputDirOrJar.exists()) return
+
         val snapshotOutputFile = outputs.file(classpathEntryInputDirOrJar.name.replace('.', '_') + "-snapshot.bin")
 
         val granularity = getClassSnapshotGranularity(classpathEntryInputDirOrJar, parameters.gradleUserHomeDir.get().asFile)