This brings the script in the repo up to date with what is being
used to generate release builds for OBS Studio on Windows, as
well as fixing up a few issues.
When using the full installer, there'll be a section where you can
choose what to install -- one section is a tree view with a "plugins"
section, and in that section there's "Browser plugin" and "Realsense
plugin". Instead of superfluously saying "plugin" for each of those,
replace with "source" instead -- so browser source and realsense source.
Also somewhat helps prevent the user from getting confused and thinking
we're installing a browser or something.
- Checks for previous instances by using the FindProcDLL NSIS plugin
- No longer allows ignoring if there is a sharing violation.
- Added version information section to allow friendly description in
the UAC elevation prompt.
- Kill lingering instances of cef-bootstrap before installing.
