Using CocoaPods with Mac Catalyst Project.

Explore to “(Project directory)”/Pods/Target Support Files/”Pods-(Project name)”

Then, you can see some files like…
“Pods-(Project name)”.debug.xcconfig” / “Pods-(Project name).release.xcconfig”

Define frameworks each platform you want to use, reference below code.

// For iOS platform.
OTHER_LDFLAGS[sdk=iphone*] = $(inherited) -l"c++" -l"sqlite3" -l"z" -framework "SOME FRAMEWORK" ...

// For macOS platform.
OTHER_LDFLAGS = $(inherited) -l"c++" -l"sqlite3" -l"z" -framework "SOME FRAMEWORK" ...