Initialize IsCoreLibrary in the constructor

Author: sharwell

src/coverlet.core/Instrumentation/Instrumenter.cs

@@ -41,16 +41,12 @@ public Instrumenter(string module, string identifier, string[] excludeFilters, s
             _includeFilters = includeFilters;
             _excludedFiles = excludedFiles ?? Array.Empty<string>();
             _excludedAttributes = excludedAttributes;
-        }
 
-        private bool IsCoreLibrary
-        {
-            get
-            {
-                return Path.GetFileNameWithoutExtension(_module) == "System.Private.CoreLib";
-            }
+            IsCoreLibrary = Path.GetFileNameWithoutExtension(_module) == "System.Private.CoreLib";
         }
 
+        private bool IsCoreLibrary { get; }
+
         public bool CanInstrument() => InstrumentationHelper.HasPdb(_module);
 
         public InstrumenterResult Instrument()