[linker] Fix reading symbols of resolved assemblies

mcs/tools/linker/Mono.Linker/LinkContext.cs

@@ -85,10 +85,7 @@ namespace Mono.Linker {
 
 		public ISymbolReaderProvider SymbolReaderProvider {
 			get { return _symbolReaderProvider; }
-			set {
-				_symbolReaderProvider = value;
-				_readerParameters.SymbolReaderProvider = value;
-			}
+			set { _symbolReaderProvider = value; }
 		}
 
 		public ISymbolWriterProvider SymbolWriterProvider {
@@ -168,6 +165,9 @@ namespace Mono.Linker {
 			if (!_linkSymbols)
 				return;
 
+			if (assembly.MainModule.HasSymbols)
+				return;
+
 			try {
 				if (_symbolReaderProvider != null) {
 					var symbolReader = _symbolReaderProvider.GetSymbolReader (