To reproduce:
- start a new project
- install latest version of burst package
- the installation will give no erros
- modify the manifest.json and add : "registry": "https://staging-packages.unity.com" to it
version1- go back to unity and wait for the package manager to finish loading

notice this error in the console afterwards:

An error occurred while resolving packages:
One or more packages could not be added to the local file system:
com.unity.burst: EPERM: operation not permitted, unlink 'E:\Unity\bupl--\Library\PackageCache\com.unity.burst@1.1.0-preview.3\.Runtime\Burst.Compiler.IL.dll'

A re-import of the project may be required to fix the issue or a manual modification of E:/Unity/bupl--/Packages/manifest.json file.

This error will not clear from the console, but it will also not keep you from going into play mode or from installing other packages.
If you restart the editor, the error will go away.
If you switch back the registry, the error will appear again.

Reproducible in 2019.3.0a8, 2019.2.0b9, 2019.1.8f1 - all with version 1.1.0 of Burst
Cannot reproduce this issue with Burst 1.0.4
Cannot reproduce in 2018.4.3f1 (because Burst version 1.1.0 is not available for that version)