Add more detail to the README

README.md

@@ -9,15 +9,25 @@ x86_64). It should run on Windows but may need the library name
 changed.
 
 ```
-make -k
+make linux-x64
 cd xxdk.NET
 dotnet run --ndf mainnet-ndf.json --state-dir world --wait 20 | grep ^DM
 ```
 
+Usually, you will want to make the library only for your
+architecture. The options are:
+
+* windows-x64
+* windows-arm64
+* linux-x64
+* linux-arm64
+* darwin-x64
+* darwin-arm64
+
 NOTE: you may need to specify a compiler to the make command, especially
 when cross compiling. Example for compiling to windows:
 ```
-CC=x86_64-w64-mingw32-gcc make -k
+CC=x86_64-w64-mingw32-gcc make windows-x64
 cd xxdk.NET
 dotnet run --ndf mainnet-ndf.json --state-dir world --wait 20 | grep ^DM
 ```