(#502) Fix path separator in nuspec file element

Converts the path separator character in the nuspec file source to the
character that is correct for the OS that is running the packing
operation. Changes "\" to "/" on Linux and MacOS systems, and
changes "/" to "\" on Windows systems.

Fixes: chocolatey/choco#502

src/Core/Authoring/ManifestReader.cs

@@ -64,7 +64,7 @@ private static ManifestMetadata ReadMetadata(XElement xElement)
             return manifestMetadata;
         }
 
-        [SuppressMessage("Microsoft.Maintainability", "CA1502:AvoidExcessiveComplexity")]    
+        [SuppressMessage("Microsoft.Maintainability", "CA1502:AvoidExcessiveComplexity")]
         private static void ReadMetadataValue(ManifestMetadata manifestMetadata, XElement element, HashSet<string> allElements)
         {
             if (element.Value == null)
@@ -151,10 +151,10 @@ private static void ReadMetadataValue(ManifestMetadata manifestMetadata, XElemen
                     break;
                 case "conflicts":
                     manifestMetadata.Conflicts = value;
-                    break;             
+                    break;
                 case "softwareDisplayName":
                     manifestMetadata.SoftwareDisplayName = value;
-                    break;        
+                    break;
                 case "softwareDisplayVersion":
                     manifestMetadata.SoftwareDisplayVersion = value;
                     break;
@@ -274,7 +274,7 @@ private static List<ManifestDependencySet> ReadDependencySets(XElement dependenc
                 return new List<ManifestDependencySet>();
             }
 
-            // Disallow the <dependencies> element to contain both <dependency> and 
+            // Disallow the <dependencies> element to contain both <dependency> and
             // <group> child elements. Unfortunately, this cannot be enforced by XSD.
             if (dependenciesElement.ElementsNoNamespace("dependency").Any() &&
                 dependenciesElement.ElementsNoNamespace("group").Any())
@@ -340,9 +340,17 @@ private static List<ManifestFile> ReadFilesList(XElement xElement)
                 string target = file.GetOptionalAttributeValue("target").SafeTrim();
                 string exclude = file.GetOptionalAttributeValue("exclude").SafeTrim();
 
-                // Multiple sources can be specified by using semi-colon separated values. 
+                char separator = Path.DirectorySeparatorChar;
+
+                // Multiple sources can be specified by using semi-colon separated values.
                 files.AddRange(from source in srcElement.Value.Trim(';').Split(';')
-                               select new ManifestFile { Source = source.SafeTrim(), Target = target.SafeTrim(), Exclude = exclude.SafeTrim() });
+                               select new ManifestFile
+                               {
+                                   // Replace directory separator in the file src element to the one that is correct for the OS of the packing system.
+                                   Source = source.SafeTrim().Replace('/', separator).Replace('\u005c', separator),
+                                   Target = target.SafeTrim(),
+                                   Exclude = exclude.SafeTrim()
+                               });
             }
             return files;
         }