/FD (IDE Minimal Rebuild)
/FD is not exposed to users except in the Command Line property page of a C++ project's Property Pages dialog box, if and only if /Gm (Enable Minimal Rebuild) is not also selected. /FD has no effect other than from the development environment. /FD is not exposed in the output of cl /?.
If you do not enable /Gm in the development environment, /FD will be used. /FD ensures that the .idb file has sufficient dependency information. /FD is only used by the development environment, and it should not be used from the command line or a build script.