Update build instructions for Linux and Mac.

README.md

@@ -54,11 +54,15 @@ Windows:
 (Optional, Windows-only) Note: If you want to use the same build configuration as the build server, you will have to install `VC++ 2017 version 15.7 v14.14 latest v141 tools` (or similar) from the "Individual components" section in the Visual Studio Setup. We use `editbin.exe` to modify the stack size used by ILSpy.exe from 1MB to 16MB, because the decompiler makes heavy use of recursion, where small stack sizes lead to problems in very complex methods.
 
 Unix:
+- Make sure .NET Core 2.2 is installed (you can get it here: https://get.dot.net).
 - Check out the repository using git.
 - Execute `git submodule update --init --recursive` to get all required submodules.
+- Use `dotnet build Frontends.sln` to build the non-Windows flavors of ILSpy (cli and powershell core).
+
+(Visual Studio for Mac users only:)
 - Edit `\ICSharpCode.Decompiler\ICSharpCode.Decompiler.csproj`
   Add `Sdk="Microsoft.NET.Sdk"` to the `Project` element.
-  This is required due to a tooling issue on Unix.
+  This is required due to a tooling issue.
   Please do not commit this when contributing a pull request!
 - Use Frontends.sln to work.