- introduce WM_COMPILE_CONTROL variable to convey control information
into the build rules.
The convention (as per spack):
- '+' to select a feature
- '~' to deselect a feature
Eg, to select the gold linker, and disable openmp
(spaces are not required):
WM_COMPILE_CONTROL="+gold ~openmp"
CONFIG: accept FOAM_EXTRA_LDFLAGS for AMD, gold, Mingw linkers
CONFIG: generalize PROJECT_LIBS (-ldl used almost universally)
