(GH-448) Keep nupkgs at end of build

When running on CI system, nupkgs will still be deleted to help with
potential storage issues, but by default, locally, the nupkgs will be
kept around, unless expressly told to delete them.

Cake.Recipe/Content/build.cake

@@ -104,7 +104,7 @@ Teardown(context =>
     }
 
     // Clear nupkg files from tools directory
-    if(DirectoryExists(Context.Environment.WorkingDirectory.Combine("tools")))
+    if((!BuildParameters.IsLocalBuild || BuildParameters.ShouldDeleteCachedFiles) && DirectoryExists(Context.Environment.WorkingDirectory.Combine("tools")))
     {
         Information("Deleting nupkg files...");
         var nupkgFiles = GetFiles(Context.Environment.WorkingDirectory.Combine("tools") + "/**/*.nupkg");

Cake.Recipe/Content/parameters.cake

@@ -99,6 +99,7 @@ public static class BuildParameters
     public static bool ShouldDownloadMilestoneReleaseNotes { get; private set;}
     public static bool ShouldDownloadFullReleaseNotes { get; private set;}
     public static bool ShouldNotifyBetaReleases { get; private set; }
+    public static bool ShouldDeleteCachedFiles { get; private set; }
 
     public static FilePath MilestoneReleaseNotesFilePath { get; private set; }
     public static FilePath FullReleaseNotesFilePath { get; private set; }
@@ -307,6 +308,7 @@ public static class BuildParameters
         context.Information("ShouldDownloadFullReleaseNotes: {0}", ShouldDownloadFullReleaseNotes);
         context.Information("ShouldDownloadMilestoneReleaseNotes: {0}", ShouldDownloadMilestoneReleaseNotes);
         context.Information("ShouldNotifyBetaReleases: {0}", ShouldNotifyBetaReleases);
+        context.Information("ShouldDeleteCachedFiles: {0}", ShouldDeleteCachedFiles);
         context.Information("ShouldGenerateDocumentation: {0}", ShouldGenerateDocumentation);
         context.Information("ShouldRunIntegrationTests: {0}", ShouldRunIntegrationTests);
         context.Information("ShouldRunGitVersion: {0}", ShouldRunGitVersion);
@@ -369,6 +371,7 @@ public static class BuildParameters
         bool shouldDownloadMilestoneReleaseNotes = false,
         bool shouldDownloadFullReleaseNotes = false,
         bool shouldNotifyBetaReleases = false,
+        bool shouldDeleteCachedFiles = false,
         FilePath milestoneReleaseNotesFilePath = null,
         FilePath fullReleaseNotesFilePath = null,
         bool shouldPublishMyGet = true,
@@ -462,6 +465,7 @@ public static class BuildParameters
         ShouldDownloadFullReleaseNotes = shouldDownloadFullReleaseNotes;
         ShouldDownloadMilestoneReleaseNotes = shouldDownloadMilestoneReleaseNotes;
         ShouldNotifyBetaReleases = shouldNotifyBetaReleases;
+        ShouldDeleteCachedFiles = shouldDeleteCachedFiles;
         ShouldRunDupFinder = shouldRunDupFinder;
         ShouldRunInspectCode = shouldRunInspectCode;
         ShouldRunCodecov = shouldRunCodecov;