buildDotnetModule: fix build for dotnet-sdk versions below 6

The --self-contained and --no-self-contained switches were
added to the dotnet build command starting with .NET 6.
The switch is equivalent to the setting the SelfContained
property, so we use the property for backwards compatibility.

pkgs/build-support/dotnet/build-dotnet-module/hooks/dotnet-build-hook.sh

@@ -15,9 +15,9 @@ dotnetBuildHook() {
     fi
 
     if [ "${selfContainedBuild-}" ]; then
-        dotnetBuildFlags+=("--self-contained")
+        dotnetBuildFlags+=("-p:SelfContained=true")
     else
-        dotnetBuildFlags+=("--no-self-contained")
+        dotnetBuildFlags+=("-p:SelfContained=false")
     fi
 
     if [ "${version-}" ]; then