search path to ${WRKDIR}/bin. Ensures that the ld wrapper script needed
for USE_WXNEEDED gets used (clang was ignoring it otherwise).
Rework ccache support and gcc4/clang MODULES to use the same wrapper
generator as above, setting up a list of command names (cc, c++, etc) and
destinations (egcc, eg++, etc) as the port is processed, and writing the
wrappers in one place in bsd.port.mk, with an optional wrapper (e.g.
ccache), and with an echo to make it clear on screen/in log which
compiler binaries were chosen (easier than inspecting the wrapper
scripts) and whether ccache is used.
Initial wrapper using -B from espie, ccache bits from me, discussed
with/ok espie. Been through a bulk on i386.
868a63b397