Preliminary support for bmake
Please note that bmake it only supported on current starting at r250164:

• make sure bmake treats -V as expected [1]
• tell bmake we use the old :L :U modifiers [1]
• workaround an incompatible loop syntax using bmake's inline loop [1]
• avoid forking a shell to get the CKSUMFILES which gives a make(1)/bmake(1) compatible syntax [2]

Submitted by: sjg[1]
Obtained from: dports[2]