Error while building mission planner

#### Issue details####
Hello, when I tried to build mission planner in Windows 10, I have 3 errors:

Error CS0579 Duplicate 'global::System.Runtime.Versioning.TargetFrameworkAttribute' attribute 7zip (netstandard2.0) C:\Users\user\source\repos\Filetest.razor\ExtLibs\7zip\Compress\LzmaAlone\obj\Release\.NETFramework,Version=v4.0.AssemblyAttributes.cs 4 Active
Error CS0579 Duplicate 'global::System.Runtime.Versioning.TargetFrameworkAttribute' attribute 7zip (netstandard2.0) C:\Users\user\source\repos\Filetest.razor\ExtLibs\7zip\obj\Debug\netstandard2.0\.NETStandard,Version=v2.0.AssemblyAttributes.cs 4 Active
Error Could not find file 'C:\Users\user\source\repos\Filetest.razor\ExtLibs\7zip\bin\Debug\net461\7zip.dll'. MissionPlanner C:\Users\user\source\repos\Filetest.razor\test\FirmwareSelection.xaml

Please help me to solve this errors. thank you.

#### Platform
[ x ] All
[ ] AntennaTracker
[ ] Copter
[ ] Plane
[ ] Rover
[ ] Sub

Start by reproducing the Windows 10 build and inspect the 7zip project output, especially the duplicate generated assembly-attribute files under obj and the missing bin\Debug\net461\7zip.dll referenced by test/FirmwareSelection.xaml. Done means the MissionPlanner build completes without CS0579 and the expected 7zip.dll is produced at the referenced path.

Written by the indexing model from the issue text.