Linking fails with "ld: 4 duplicate symbols for architecture x86_64"

[RandoNandoz]

I disabled code signing, and built the project using Xcode 12.

The build fails, with "duplicate symbols"

Ld /Users/randyzhu/builds/Release/smcFanControl.app/Contents/MacOS/smcFanControl normal (in target 'smcFanControl' from project 'smcFanControl')
    cd /Users/randyzhu/Downloads/smcFanControl
    /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/clang -target x86_64-apple-macos10.7 -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX11.1.sdk -L/Users/randyzhu/builds/Release -L/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX11.1.sdk/usr/lib/system -F/Users/randyzhu/builds/Release -F/Users/randyzhu/Downloads/smcFanControl -F/Users/randyzhu/Downloads/smcFanControl -filelist /Users/randyzhu/builds/smcFanControl.build/Release/smcFanControl.build/Objects-normal/x86_64/smcFanControl.LinkFileList -Xlinker -rpath -Xlinker @loader_path/../Frameworks -fobjc-arc -fobjc-link-runtime -framework Sparkle -framework Cocoa -framework IOKit -framework Security -framework WebKit -Xlinker -no_adhoc_codesign -Xlinker -dependency_info -Xlinker /Users/randyzhu/builds/smcFanControl.build/Release/smcFanControl.build/Objects-normal/x86_64/smcFanControl_dependency_info.dat -o /Users/randyzhu/builds/Release/smcFanControl.app/Contents/MacOS/smcFanControl

duplicate symbol '_fannum' in:
    /Users/randyzhu/builds/smcFanControl.build/Release/smcFanControl.build/Objects-normal/x86_64/main.o
    /Users/randyzhu/builds/smcFanControl.build/Release/smcFanControl.build/Objects-normal/x86_64/FanControl.o
duplicate symbol '_fannum' in:
    /Users/randyzhu/builds/smcFanControl.build/Release/smcFanControl.build/Objects-normal/x86_64/main.o
    /Users/randyzhu/builds/smcFanControl.build/Release/smcFanControl.build/Objects-normal/x86_64/smc.o
duplicate symbol '_fannum' in:
    /Users/randyzhu/builds/smcFanControl.build/Release/smcFanControl.build/Objects-normal/x86_64/main.o
    /Users/randyzhu/builds/smcFanControl.build/Release/smcFanControl.build/Objects-normal/x86_64/smcWrapper.o
duplicate symbol '_fannum' in:
    /Users/randyzhu/builds/smcFanControl.build/Release/smcFanControl.build/Objects-normal/x86_64/main.o
    /Users/randyzhu/builds/smcFanControl.build/Release/smcFanControl.build/Objects-normal/x86_64/MachineDefaults.o
ld: 4 duplicate symbols for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)