Fix Microsoft.NETCore.Platforms builds on Unix (#57739)

ViktorHofer · web-flow · commit f169b71c5403 · 2021-08-19T20:38:12.000+02:00
The casing of the SDK imported via the Sdk attribute was wrong which lead to:

Microsoft.NETCore.Platforms.csproj : error MSB4236: The SDK 'Microsoft.NET.SDK' specified could not be found.
diff --git a/src/libraries/Microsoft.NETCore.Platforms/src/Microsoft.NETCore.Platforms.csproj b/src/libraries/Microsoft.NETCore.Platforms/src/Microsoft.NETCore.Platforms.csproj
@@ -1,4 +1,4 @@
-<Project Sdk="Microsoft.NET.SDK">
+<Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
     <TargetFrameworks>$(NetCoreAppToolCurrent);net472</TargetFrameworks>
     <!-- This project should not build against the live built .NETCoreApp targeting pack as it contributes to the build itself. -->

Original file line number	Diff line number	Diff line change
`@@ -1,4 +1,4 @@`
`1`		`-<Project Sdk="Microsoft.NET.SDK">`
	`1`	`+<Project Sdk="Microsoft.NET.Sdk">`
`2`	`2`	`<PropertyGroup>`
`3`	`3`	`<TargetFrameworks>$(NetCoreAppToolCurrent);net472</TargetFrameworks>`
`4`	`4`	`<!-- This project should not build against the live built .NETCoreApp targeting pack as it contributes to the build itself. -->`