Show warnings for disabled targets on current host

Issue #KT-26647 Fixed

konan/utils/src/org/jetbrains/kotlin/konan/target/KonanTarget.kt

@@ -173,34 +173,34 @@ open class HostManager(subtargetProvider: SubTargetProvider = NoSubTargets()) {
     }
 
     val enabled: List<KonanTarget> by lazy {
-        when (host) {
+        enabledTargetsByHost[host]?.toList() ?: throw TargetSupportException("Unknown host platform: $host")
-            KonanTarget.LINUX_X64 -> listOf(
-                KonanTarget.LINUX_X64,
-                KonanTarget.LINUX_ARM32_HFP,
-                KonanTarget.LINUX_MIPS32,
-                KonanTarget.LINUX_MIPSEL32,
-                KonanTarget.ANDROID_ARM32,
-                KonanTarget.ANDROID_ARM64,
-                KonanTarget.WASM32
-            ) + zephyrSubtargets
-            KonanTarget.MINGW_X64 -> listOf(
-                KonanTarget.MINGW_X64,
-                KonanTarget.WASM32
-            ) + zephyrSubtargets
-            KonanTarget.MACOS_X64 -> listOf(
-                KonanTarget.MACOS_X64,
-                KonanTarget.IOS_ARM32,
-                KonanTarget.IOS_ARM64,
-                KonanTarget.IOS_X64,
-                KonanTarget.ANDROID_ARM32,
-                KonanTarget.ANDROID_ARM64,
-                KonanTarget.WASM32
-            ) + zephyrSubtargets
-            else ->
-                throw TargetSupportException("Unknown host platform: $host")
-        }
     }
 
+    val enabledTargetsByHost = mapOf(
+        KonanTarget.LINUX_X64 to setOf(
+            KonanTarget.LINUX_X64,
+            KonanTarget.LINUX_ARM32_HFP,
+            KonanTarget.LINUX_MIPS32,
+            KonanTarget.LINUX_MIPSEL32,
+            KonanTarget.ANDROID_ARM32,
+            KonanTarget.ANDROID_ARM64,
+            KonanTarget.WASM32
+        ) + zephyrSubtargets,
+        KonanTarget.MINGW_X64 to setOf(
+            KonanTarget.MINGW_X64,
+            KonanTarget.WASM32
+        ) + zephyrSubtargets,
+        KonanTarget.MACOS_X64 to setOf(
+            KonanTarget.MACOS_X64,
+            KonanTarget.IOS_ARM32,
+            KonanTarget.IOS_ARM64,
+            KonanTarget.IOS_X64,
+            KonanTarget.ANDROID_ARM32,
+            KonanTarget.ANDROID_ARM64,
+            KonanTarget.WASM32
+        ) + zephyrSubtargets
+    )
+
     fun isEnabled(target: KonanTarget) = enabled.contains(target)
 
     companion object {

libraries/tools/kotlin-gradle-plugin/src/main/kotlin/org/jetbrains/kotlin/gradle/plugin/mpp/kotlinTargetPresets.kt

@@ -324,6 +324,20 @@ class KotlinNativeTargetPreset(
             }
         }
 
+        if (!konanTarget.enabledOnCurrentHost) {
+            with(HostManager()) {
+                val supportedHosts = enabledTargetsByHost.filterValues { konanTarget in it }.keys
+                val supportedHostsString =
+                    if (supportedHosts.size == 1)
+                        "a ${supportedHosts.single()} host" else
+                        "one of the host platforms: ${supportedHosts.joinToString(", ")}"
+                project.logger.warn(
+                    "Target '$name' for platform ${konanTarget} is ignored during build on this ${HostManager.host} machine. " +
+                            "You can build it with $supportedHostsString."
+                )
+            }
+        }
+
         return result
     }