[CMake] CMake, JOM and multiple top-level targets

[Óscar Fuentes]

JOM does a nice work compiling multiple files of the same top-level
product (.exe, .dll etc) but for some reason it doesn't build multiple
top-level targets in parallel. Here I have a project that generates
several independent dlls, each based on one or two source files. JOM
wont build DLL_N+1 until DLL_N is finished. This means that only one cpu
core is working for a long part of the build.

Is this a limitation of JOM or an oversight of CMake?