MSBuild 16.11.0

This version of MSBuild shipped with Visual Studio 2019 version 16.11.0 and .NET SDK 5.0.400.

What's new

MSBuild now supports long paths in the 64-bit amd64\MSBuild.exe executable.
New version properties MSBuildFileVersion (4-part, matches file version) and MSBuildSemanticVersion (matches package versions) are now available for use (#6534).

Additional properties documented and available for completion in Visual Studio (#6500, #6530).
The SignFile task is now available in MSBuild on .NET 5.0 (#6509). Thanks, @Zastai!
New version properties MSBuildFileVersion (4-part, matches file version) and MSBuildSemanticVersion (matches package versions) are now available for use (#6534).

When using the experimental cache API, schedule proxy builds to the in-proc node for performance (#6386).
Experimental cache queries are now executed in parallel (#6468).
The ETW events generated in ResolveAssemblyReference now include an approximation of the "size" of the RAR request (#6410).

Fixed memory leak in ProjectRootElement.Reload (#6457).
Added locking to avoid race conditions in BuildManager (#6412).
Allow ResolveAssemblyReferences precomputed cache files to be in read-only locations (#6393).
64-bit al.exe is used when targeting 64-bit architectures (for real this time) (#6484).
Builds with ProduceOnlyReferenceAssembly no longer expect debug symbols to be produced (#6511). Thanks, @Zastai!
64-bit MSBuild.exe supports long paths (and other .NET default behaviors) (#6562).
Non-graph builds no longer crash in the experimental project cache (#6568).
The experimental project cache is initialized only once (#6569).
The experimental project cache no longer tries to schedule proxy builds to the in-proc node (#6635).

Use a packaged C# compiler to avoid changes in reference assembly generation caused by compiler changes (#6431).
Use more resilient test-result upload patterns (#6489).
Conditional compilation for .NET Core within our repo now includes new .NET 5.0+ runtimes (#6538).
Switched to OneLocBuild for localization PRs (#6561).
Moved to latest Ubuntu image for PR test legs (#6573).