Driver does not handle single-file `-c -o` correctly when doing multiple frontend invocations

If you specify a single-file compilation job that requires multiple frontend invocations, such as swiftc -emit-module-path foo.swiftmodule -c -o foo.o foo.swift to simultaneously emit a module and an object output, then the driver ignores the -o flag. Passing -force-single-frontend-invocation works around this.