Update FSharp.Core package version to 4.2.1 (#3177)

src/FSharpSource.Settings.targets

@@ -45,6 +45,9 @@
     <!-- Always qualify the IntermediateOutputPath by the TargetDotnetProfile if any exists -->
     <IntermediateOutputPath>obj\$(Configuration)\$(TargetDotnetProfile)\</IntermediateOutputPath>
     <IntermediateOutputPath Condition="'$(PortableProfileBeingReferenced)' != ''">obj\$(Configuration)\$(TargetDotnetProfile)\$(PortableProfileBeingReferenced)\</IntermediateOutputPath>
+
+    <FSharpCore41Version>4.1.18</FSharpCore41Version>
+    <FSharpCore42Version>4.2.1</FSharpCore42Version>
   </PropertyGroup>
 
   <PropertyGroup Condition="'$(MonoPackaging)' != 'true' AND '$(OS)' != 'Unix'">

src/fsharp/FSharp.Core.nuget/FSharp.Core.nuget.proj

@@ -42,8 +42,8 @@
 
     <PropertyGroup>
       <PackageVersion>X.X.XXX</PackageVersion>
-      <PackageVersion Condition="'@(PackageNuspec)' != 'FSharp.Core.4.1.xxx.nuspec'">4.1.18</PackageVersion>
-      <PackageVersion Condition="'@(PackageNuspec)' != 'FSharp.Core.4.2.xxx.nuspec'">4.2.0</PackageVersion>
+      <PackageVersion Condition="'@(PackageNuspec)' != 'FSharp.Core.4.1.xxx.nuspec'">$(FSharpCore41Version)</PackageVersion>
+      <PackageVersion Condition="'@(PackageNuspec)' != 'FSharp.Core.4.2.xxx.nuspec'">$(FSharpCore42Version)</PackageVersion>
       <PackageProperties>-prop "licenseUrl=$(PackageLicenceUrl)" -prop "version=$(PackageVersion)" -prop "authors=$(PackageAuthors)" -prop "projectUrl=$(PackageProjectUrl)" -prop "tags=$(PackageTags)"</PackageProperties>
     </PropertyGroup>