[link stage][macos] forcebly mute dsymutil warning about absence of _main symbol.

backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/LinkStage.kt

@@ -16,6 +16,7 @@
 
 package org.jetbrains.kotlin.backend.konan
 
+import org.jetbrains.kotlin.backend.konan.util.bufferedReader
 import java.io.File
 import java.lang.ProcessBuilder
 import java.lang.ProcessBuilder.Redirect
@@ -93,7 +94,7 @@ internal open class MacOSBasedPlatform(distribution: Distribution)
 
     // TODO: move 'ld' out of the host sysroot, as it doesn't belong here.
     private val linker = "${distribution.hostSysRoot}/usr/bin/ld"
-    private val dsymutil = "${distribution.llvmBin}/llvm-dsymutil"
+    internal val dsymutil = "${distribution.llvmBin}/llvm-dsymutil"
 
     open val osVersionMin by lazy {
         listOf(
@@ -277,11 +278,29 @@ internal class LinkStage(val context: Context) {
         val builder = ProcessBuilder(command.asList())
 
         // Inherit main process output streams.
+        val isDsymUtil = platform is MacOSBasedPlatform && command[0] == platform.dsymutil
+
         builder.redirectOutput(Redirect.INHERIT)
         builder.redirectInput(Redirect.INHERIT)
-        builder.redirectError(Redirect.INHERIT)
+        if (!isDsymUtil)
+            builder.redirectError(Redirect.INHERIT)
+
 
         val process = builder.start()
+        if (isDsymUtil) {
+            /**
+             * llvm-lto has option -alias that lets tool to know which symbol we use instead of _main,
+             * llvm-dsym doesn't have such a option, so we ignore annoying warning manually.
+             */
+            val errorStream = process.errorStream
+            val outputStream = bufferedReader(errorStream)
+            while (true) {
+                val line = outputStream.readLine() ?: break
+                if (!line.contains("warning: could not find object file symbol for symbol _main"))
+                    System.err.println(line)
+            }
+            outputStream.close()
+        }
         val exitCode =  process.waitFor()
         return exitCode
     }

backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/util/NoJavaUtil.kt

@@ -16,6 +16,9 @@
 
 package org.jetbrains.kotlin.backend.konan.util
 
+import java.io.BufferedReader
+import java.io.InputStream
+import java.io.InputStreamReader
 import java.net.URI
 import java.nio.file.FileSystems
 import java.nio.file.Files
@@ -118,3 +121,4 @@ fun File.copyTo(destination: File, vararg options: StandardCopyOption) {
     Files.copy(this.toPath(), destination.toPath(), *options) 
 }
 
+fun bufferedReader(errorStream: InputStream?) = BufferedReader(InputStreamReader(errorStream))