Fix non ascii character handling

Fixes mojohausgh-158

src/main/java/org/codehaus/mojo/exec/LineRedirectOutputStream.java

@@ -19,7 +19,12 @@
  * under the License.
  */
 
+import java.io.ByteArrayOutputStream;
 import java.io.OutputStream;
+import java.nio.charset.Charset;
+import java.nio.charset.StandardCharsets;
+import java.util.ArrayList;
+import java.util.List;
 import java.util.function.Consumer;
 
 /**
@@ -32,8 +37,8 @@
  */
 class LineRedirectOutputStream extends OutputStream {
 
-    private StringBuilder currentLine = new StringBuilder();
     private final Consumer<String> linePrinter;
+    private ByteArrayOutputStream buffer = new ByteArrayOutputStream();
 
     public LineRedirectOutputStream(Consumer<String> linePrinter) {
         this.linePrinter = linePrinter;
@@ -45,18 +50,23 @@ public void write(final int b) {
             printAndReset();
             return;
         }
-        currentLine.append((char) b);
+        buffer.write(b);
     }
 
     @Override
     public void flush() {
-        if (currentLine.length() > 0) {
+        if (buffer.size() > 0) {
             printAndReset();
         }
     }
 
+    @Override
+    public void close() {
+        flush();
+    }
+
     private void printAndReset() {
-        linePrinter.accept(currentLine.toString());
-        currentLine = new StringBuilder();
+        linePrinter.accept(new String(buffer.toByteArray(), Charset.defaultCharset()));
+        buffer = new ByteArrayOutputStream();
     }
 }

src/test/java/org/codehaus/mojo/exec/LineRedirectOutputStreamTest.java

@@ -0,0 +1,23 @@
+package org.codehaus.mojo.exec;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+import java.io.IOException;
+import java.nio.charset.Charset;
+
+public class LineRedirectOutputStreamTest {
+
+    @Test
+    public void givenUtf8Output_whenRedirecting_thenShouldDecodeProperly() throws IOException {
+        StringBuilder sb = new StringBuilder();
+        String firstLine = "Hello 😃 😄";
+        String secondLine = "foo bar éà";
+
+        try (LineRedirectOutputStream os = new LineRedirectOutputStream(sb::append)) {
+            os.write(String.join("\n", firstLine, secondLine).getBytes(Charset.defaultCharset()));
+        }
+
+        Assert.assertEquals(firstLine + secondLine, sb.toString());
+    }
+}