Revert. Uses openjdk.

src/javac-ref/javac-ref.msbuildproj

@@ -26,11 +26,10 @@
     <!-- javac-ref uses the javac executable from JAVA_HOME: bootstrap -->
     <Target Name="ResolveJavaCompiler" Condition=" '$(JAVA_HOME)' != '' And '$(JavaCompilerPath)' == '' ">
         <PropertyGroup>
-            <JavaCompilerPath Condition=" $([MSBuild]::IsOSUnixLike()) And '$(JavaCompilerPath)' == '' And Exists('$(_JavaCompilerPublishDir)javac') ">$([System.IO.Path]::GetFullPath('$(_JavaCompilerPublishDir)\javac'))</JavaCompilerPath>
-            <JavaCompilerPath Condition=" '$(JavaCompilerPath)' == '' And Exists('$(_JavaCompilerPublishDir)javac.exe') ">$([System.IO.Path]::GetFullPath('$(_JavaCompilerPublishDir)\javac.exe'))</JavaCompilerPath>
+            <JavaCompilerPath Condition=" '$([MSBuild]::IsOSUnixLike())' == 'true' And Exists('$(JAVA_HOME)\bin\javac') ">$([System.IO.Path]::GetFullPath('$(JAVA_HOME)\bin\javac'))</JavaCompilerPath>
+            <JavaCompilerPath Condition=" '$([MSBuild]::IsOSUnixLike())' != 'true' And Exists('$(JAVA_HOME)\bin\javac.exe') ">$([System.IO.Path]::GetFullPath('$(JAVA_HOME)\bin\javac.exe'))</JavaCompilerPath>
             <JavaCompilerArgs>-J-Xmx1536M</JavaCompilerArgs>
-            <JavaCompilerExec Condition=" '$(JavaCompilerExec)' == '' And $([MSBuild]::IsOSUnixLike()) And '$([System.IO.Path]::GetExtension($(JavaCompilerPath)))' == '.exe' ">mono $(JavaCompilerPath) $(JavaCompilerArgs)</JavaCompilerExec>
-            <JavaCompilerExec Condition=" '$(JavaCompilerExec)' == '' ">$(JavaCompilerPath) $(JavaCompilerArgs)</JavaCompilerExec>
+            <JavaCompilerExec Condition=" '$(JavaCompilerPath)' != '' ">"$(JavaCompilerPath)" $(JavaCompilerArgs)</JavaCompilerExec>
         </PropertyGroup>
         <Message Text="Using javac executable found in JAVA_HOME at '$(JavaCompilerPath)'." Importance="high" Condition=" '$(JavaCompilerPath)' != '' " />
     </Target>