Update dependencies from https://github.com/dotnet/source-build-externals build 20230518.1 (#48358)

[main] Update dependencies from dotnet/source-build-externals

eng/Version.Details.xml

@@ -181,9 +181,9 @@
       <Uri>https://github.com/dotnet/runtime</Uri>
       <Sha>ba775cd50984e0a0fa06526f74feb2c95ace237e</Sha>
     </Dependency>
-    <Dependency Name="Microsoft.SourceBuild.Intermediate.source-build-externals" Version="8.0.0-alpha.1.23262.1">
+    <Dependency Name="Microsoft.SourceBuild.Intermediate.source-build-externals" Version="8.0.0-alpha.1.23268.1">
       <Uri>https://github.com/dotnet/source-build-externals</Uri>
-      <Sha>a1460948fd0a4ab66b885c1575b085af70139e9a</Sha>
+      <Sha>21d564f9e16f7986d8af0692258afb91a52dda80</Sha>
       <SourceBuild RepoName="source-build-externals" ManagedOnly="true" />
     </Dependency>
     <Dependency Name="System.Configuration.ConfigurationManager" Version="8.0.0-preview.5.23271.5">

eng/Versions.props

@@ -152,7 +152,7 @@
     <!-- Packages from dotnet/source-link -->
     <MicrosoftSourceLinkGitHubVersion>8.0.0-beta.23218.3</MicrosoftSourceLinkGitHubVersion>
     <!-- Packages from dotnet/source-build-externals -->
-    <MicrosoftSourceBuildIntermediatesourcebuildexternalsVersion>8.0.0-alpha.1.23262.1</MicrosoftSourceBuildIntermediatesourcebuildexternalsVersion>
+    <MicrosoftSourceBuildIntermediatesourcebuildexternalsVersion>8.0.0-alpha.1.23268.1</MicrosoftSourceBuildIntermediatesourcebuildexternalsVersion>
     <!-- Packages from dotnet/source-build-reference-packages -->
     <MicrosoftSourceBuildIntermediatesourcebuildreferencepackagesVersion>8.0.0-alpha.1.23272.1</MicrosoftSourceBuildIntermediatesourcebuildreferencepackagesVersion>
     <!-- Packages from dotnet/xdt -->