Build updates.

Build/Targets/PackageProperties.targets

@@ -1,6 +1,7 @@
 <Project>
 
     <PropertyGroup>
+        <PackageVersion Condition="'$(PackageVersionSuffix)' != ''">$(PackageVersion)$(PackageVersionSuffix)</PackageVersion>
         <PackageDescription Condition="'$(PackageDescription)' != ''">$(PackageDescription)
 
 $(CosmosDescription)</PackageDescription>

Directory.Build.props

@@ -12,6 +12,20 @@
         <XSharpRepoRoot>$(RepoRoot)..\XSharp\</XSharpRepoRoot>
     </PropertyGroup>
 
+    <PropertyGroup>
+        <PackageVersion>0.1.0</PackageVersion>
+        <PackageVersionSuffix Condition="'$(APPVEYOR)' == 'True'">-build$(APPVEYOR_BUILD_NUMBER)+$(APPVEYOR_REPO_COMMIT.Substring(0, 7))</PackageVersionSuffix>
+        <!--
+            If it's a design-time build, we can't use current time, because it can
+            cause an infinite restore loop, as the property is always changing.
+            This means that, for project references in VS (and other IDEs), the
+            resolved version will be the stable one, i.e. without the
+            -localbuildyyyyMMddhhmmss suffix.
+        -->
+        <PackageVersionSuffix Condition="'$(PackageVersionSuffix)' == '' AND '$(DesignTimeBuild)' != 'True'">-localbuild$([System.DateTime]::Now.ToString("yyyyMMddhhmmss"))</PackageVersionSuffix>
+        <PackageVersionSuffix Condition="'$(APPVEYOR_REPO_TAG)' == 'True'"></PackageVersionSuffix>
+    </PropertyGroup>
+
     <PropertyGroup>
         <CommonVersion>0.1.0-build8</CommonVersion>
         <IL2CPUVersion>0.1.0-build328</IL2CPUVersion>