參閲：http://www.mono-PRoject.com/archived/porting_msbuild_projects_to_xbuild/

Pre/PostBuildEvents

These events contain shell commands to be run before or after a build. They are executed using the shell, cmd.exe on Windows and typically sh on Unix. Shell command for Windows won’t run on linux or Mac, but to solve this, you could add more conditional Pre/PostBuildEvents, like:

   <PreBuildEvent Condition=" '$(OS)' == 'Unix' ">cp foo.txt $(OutDir)/foo.txt</PreBuildEvent>   <PreBuildEvent Condition=" '$(OS)' != 'Unix' ">copy foo.txt $(OutDir)/foo.txt</PreBuildEvent>
The condition could be based on the Configuration also, for example you could create a new “Unix” configuration.
Another, way of doing this could be to use the Before/AfterBuild targets, with which you can use the built-in tasks, like “Copy”, “MakeDir” etc, so no problem with portability. Eg:
 <Target Name="BeforeBuild">          <Copy SourceFiles="foo.txt" DestinationFolder="$(OutDir)" /> </Target>
For commands that have no corresponding tasks available and you don’t want to write a custom task for them, you can use the ‘Exec’ task, which invokes the specified ‘Command’ using the shell.
 <Target Name="AfterBuild">          <Exec Command="foo.exe arg1 arg2" Condition=" '$(OS)' == 'Windows_NT' " /> </Target>