$< isn't supported in BSD make say. $(RM) is pre-defined in GNU make
though, not in BSD make say. so changed to check on configure if it's
pre-defined by make, otherwise set the appropriate command to $(RM).
This would be a workaround until it has the certain pre-defined value.
The filtering, '%{+elt1,elt2,elt3{subexpr}}' will evaluate subexpr
with a pattern only having the listed elements from the surrounding
pattern.
The deletion, '%{-elt1,elt2,elt3{subexpr}}' will evaluate subexpr
with a the surrounding pattern sans the listed elements.
Akira TAGOH
Behdad Esfahbod