Support environment variable expansion in the RudeBuild cache path, s…

…o you can now set it to something like %TEMP%\RudeBuildCache.

src/RudeBuild/ProjectInfo.cs

@@ -66,6 +66,18 @@ private static int GetPathAttribute(string path)
 
 			throw new FileNotFoundException();
 		}
+		public static string ExpandEnvironmentVariables(string value)
+		{
+			if (string.IsNullOrEmpty(value))
+				return value;
+
+			foreach (DictionaryEntry environmentVariable in Environment.GetEnvironmentVariables())
+			{
+				value = value.Replace("%" + (string)environmentVariable.Key + "%", (string)environmentVariable.Value, StringComparison.OrdinalIgnoreCase);
+			}
+
+			return value;
+		}
 	}
 
 	public class ProjectInfo

src/RudeBuild/Settings.cs

@@ -64,7 +64,7 @@ public string GetCachePath(SolutionInfo solutionInfo)
             string solutionDirectory = solutionInfo.Name + "_" + GetMD5Hash(solutionInfo.FilePath);
             string config = BuildOptions.Config.Replace('|', '-');
 
-            string cachePath = Path.Combine(GlobalSettings.CachePath, solutionDirectory);
+            string cachePath = Path.Combine(PathHelpers.ExpandEnvironmentVariables(GlobalSettings.CachePath), solutionDirectory);
             cachePath = Path.Combine(cachePath, config);
             return cachePath;
         }