How odd. I haven't used Angleproject before, but I've never heard of a problem occurring in VS builds with just a single file out of a project
- usually such issues occur on a project-by-project basis. (Unless BuiltInFunctionEmulator.cpp is the only .cpp in that project?)
Anyway, (sadly) usually the first thing to try with weird VS build issues is to do a clean build, in case its internal dependency information is corrupted somehow. In VS, go to Build -> Batch Build, click Select All and then Clean. This will wipe out the built files for all platforms and configurations. Then try to build the desired platform/configuration again.
If it still doesn't work, try poking around in the project properties - right-click on the project node in Solution Explorer and choose Properties. Look specifically at the output/intermediate paths and names in the General tab - you should see something like \\$(Platform)\\\$(Configuration), which means it will generate paths like x64\Debug. It may have been changed from the defaults. The project properties can also vary per platform and configuration (see the dropdowns at the top of the properties dialog), so it's possible someone meant to change it for x64 and accidentally changed it for x86 as well, or some such.
Another place to look is in Build -> Configuration Manager. That sets which project configurations are built for each solution configuration. It's possible something is messed up there too (e.g. the x64 solution configuration builds the project in x86 or some such).