I've given up on the parallel build facility in VCBUILD (the /M option, such as /M2). It is almost useless for our build scenario. Instead I've switched to GNU make from the "cygwin" project. GNU make supports the -j command line parameter to enable parallel builds. GNU make also allows me to specify dependencies at whatever granularity level I need. Currently I specify dependencies on a per-project basis (one project = one .vcproj file), but I could just as easily go one level deeper and have multiple dependencies for each project, such as Debug/Release/Demo.
My makefile looks something like this (simplified for demonstration purposes):
all: sdk gui server
This makefile is launched by a batch file that sets two very important environment variables:
By setting the "SolutionPath" environment variable to the solution file, we give VCBUILD the ability to set the $(SolutionDir) variable in the build scripts, which is typically required to build successfully.
When you point VCBUILD at a vcproj file, it automatically builds all configurations in that file. This way the makefile doesn't need to have knowledge of all the possible configurations. One feature you give up by specifying the vcproj file is that VCBUILD won't automatically add dependent libraries to the link line. For Visual Studio, this isn't a loss because the feature is largely broken anyway.
Using GNU make gives me the control that I need to keep my dual core processor busy. I'm finally happy :-)