in particular to pick-up the DebugSwitches from system/controlDict at
global construction time.
Disadvantage is that system/controlDict is only picked-up if the
OpenFOAM application is executed IN the case directory. The directory
provided by the -case option is not yet known as the arguments have not
yet been parsed.
To compile with 64bit labels set
WM_LABEL_SIZE=64
in ~/OpenFOAM/dev/prefs.sh
source ~/.bashrc
then Allwmake in OpenFOAM-dev.
This will build into for example OpenFOAM-dev/platforms/linux64ClangDPInt64Opt
If WM_LABEL_SIZE is unset or set to 32:
WM_LABEL_SIZE=32
the build would be placed into OpenFOAM-dev/platforms/linux64ClangDPInt32Opt
Thus both 32bit and 64bit label builds can coexist without problem.