Fix .binlog archiving

A second '/bl' parameter to msbuild looks to have been causing the filename specified in the first one to be ignored,
which meant the log filename didn't match what was set up in the build definition

eng/build.yml

@@ -66,7 +66,7 @@ phases:
         SourceFolder: '$(Build.SourcesDirectory)'
         Contents: |
          msbuild.log
-         msbuild.mainbuild.binlog
+         msbuild.binlog
          msbuild.generatepropsfile.binlog
         TargetFolder: '$(Build.ArtifactStagingDirectory)'
       continueOnError: true

run-build.ps1

@@ -113,6 +113,6 @@ if ($NoBuild)
 else
 {
     dotnet msbuild build.proj /bl:msbuild.generatepropsfile.binlog /p:Architecture=$Architecture /p:GeneratePropsFile=true /t:WriteDynamicPropsToStaticPropsFiles $ExtraParametersNoTargets
-    dotnet msbuild build.proj /bl:msbuild.mainbuild.binlog /m /v:normal /fl /flp:v=diag /bl /p:Architecture=$Architecture $ExtraParameters
+    dotnet msbuild build.proj /m /v:normal /fl /flp:v=diag /bl /p:Architecture=$Architecture $ExtraParameters
     if($LASTEXITCODE -ne 0) { throw "Failed to build" } 
 }