Prevent invalid versions

Discord.Net.targets

@@ -15,7 +15,7 @@
     </PropertyGroup>
     <PropertyGroup Condition=" '$(BuildNumber)' != '' And $(IsTagBuild) != 'true' ">
         <VersionSuffix Condition=" '$(VersionSuffix)' != '' ">$(VersionSuffix)-$(BuildNumber)</VersionSuffix>
-        <VersionSuffix Condition=" '$(VersionSuffix)' == '' ">$(BuildNumber)</VersionSuffix>
+        <VersionSuffix Condition=" '$(VersionSuffix)' == '' ">build-$(BuildNumber)</VersionSuffix>
     </PropertyGroup>
     <PropertyGroup Condition=" '$(TargetFramework)' == 'netstandard1.3' Or '$(TargetFramework)' == 'net45' ">
         <DefineConstants>$(DefineConstants);FILESYSTEM;DEFAULTUDPCLIENT;DEFAULTWEBSOCKET</DefineConstants>