Fix duplicate target error when building MSI

[speth]

Changes proposed in this pull request

MSI builds (see here) are currently failing with the error:

scons: *** Two different builders (<class 'SCons.Builder.BuilderBase'> and InstallBuilder) were specified for the same target: include\cantera\base\config.h
File "D:\a\cantera-windows-binaries\cantera-windows-binaries\cantera\site_scons\site_tools\recursiveInstall.py", line 52, in RecursiveInstall

This PR fixes this error.

Checklist

• The pull request includes a clear description of this code change
• Commit messages have short titles and reference relevant issues
• Build passes (scons build & scons test) and unit tests address code coverage
• Style & formatting of contributed code follows contributing guidelines
• The pull request is ready for review