[gradle, mpp] Clean-up dead code around metadata klib manifest handling

See the added source comment for details. This commit shouldn't change
any behavior of KGP

^KT-64525

libraries/tools/kotlin-gradle-plugin/src/common/kotlin/org/jetbrains/kotlin/gradle/targets/native/tasks/KotlinNativeTasks.kt

@@ -271,16 +271,6 @@ abstract class AbstractKotlinNativeCompile<
         compilation.languageSettings
     }
 
-    @get:Input
-    @get:Optional
-    internal val konanTargetsForManifest: String by project.provider {
-        @Suppress("CAST_NEVER_SUCCEEDS") // TODO: this warning looks very suspicious, as if the code never works as intended.
-        (compilation as? KotlinSharedNativeCompilation)
-            ?.konanTargets
-            ?.joinToString(separator = " ") { it.visibleName }
-            .orEmpty()
-    }
-
     @get:Internal
     internal val manifestFile: Provider<RegularFile> get() = projectLayout.buildDirectory.file("tmp/$name/inputManifest")
 
@@ -504,7 +494,25 @@ internal constructor(
         val manifestFile: File = manifestFile.get().asFile
         manifestFile.ensureParentDirsCreated()
         val properties = java.util.Properties()
-        properties[KLIB_PROPERTY_NATIVE_TARGETS] = konanTargetsForManifest
+        /**
+         * We're overwriting the native_targets field in the klib manifest, because otherwise it will contain
+         * only one passed `-target` or host-target, if nothing is passed. Both options are wrong for shared-native
+         * compilations.
+         *
+         * If the native_targets manifest will contain too few targets, IDE and compilation will not work properly (e.g., it will forbid
+         * dependencies on such metadata-klibs from shared native source sets, because it will consider that a source set with targets
+         * like (iosArm64, iosSimulatorArm64) can't depend on a klib with native_targets=iosArm64)
+         *
+         * Now, overwriting it to empty value is entirely unintended behavior that appeared long time ago (~Kotlin 1.4) due to some
+         * unfortunate merges. Surprisingly, it gives the desired behavior.
+         *
+         * While we could change this code to contain the proper set of KonanTargets (the ones that are actually the targets of shared-native
+         * compilation), that would introduce one new "flavour" of manifests/binaries, which complicates a bit further work in this area.
+         *
+         * So, for now we're leaving this "hack" as is. Refer to KT-64525 "Clean-up target-related fields in manifest of klibs" for the
+         * plan on proper fixes
+         */
+        properties[KLIB_PROPERTY_NATIVE_TARGETS] = ""
         properties.saveToFile(org.jetbrains.kotlin.konan.file.File(manifestFile.toPath()))
 
         return SharedCompilationData(manifestFile, refinesModule)