Update source build to latest 17.8 version

Author: marcpopMSFT

src/SourceBuild/content/eng/Versions.props

@@ -28,7 +28,7 @@
     <!-- command-line-api dependencies -->
     <SystemCommandLineVersion>2.0.0-beta4.24126.1</SystemCommandLineVersion>
     <!-- msbuild dependencies -->
-    <MicrosoftBuildVersion>17.8.3</MicrosoftBuildVersion>
+    <MicrosoftBuildVersion>17.8.29</MicrosoftBuildVersion>
     <!-- runtime dependencies -->
     <MicrosoftExtensionsFileSystemGlobbingVersion>8.0.0</MicrosoftExtensionsFileSystemGlobbingVersion>
     <MicrosoftExtensionsLoggingConsoleVersion>8.0.0</MicrosoftExtensionsLoggingConsoleVersion>