vs2010 (and above) has an issue where if the vcxproj file
isn't modified but the.vcxproj.filters is modified during
premake, then VS doesn't notify the user that the project has
changed. This can occur if the only change to a project is
with the vpaths. Before this fix, the user would be need to
manually unload and reload the project to pick up the change.
This VS workaround checks for the case where the vcxproj.filters
file is modified but the .vcxproj file is not. At which point
premake preforms a touch on the .vcxproj file to trigger the IDE.
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