ipv6calc @1.0.0 does not honor MacPorts CFLAGS or LDFLAGS

[ryandesign (Ryan Carsten Schmidt)]

The configure script proudly prints out the CFLAGS and LDFLAGS we've requested:

*** CFLAGS                     =-pipe -Os -arch x86_64 -arch i386
*** LDFLAGS                    =-L/opt/local/lib -Wl,-headerpad_max_install_names -arch x86_64 -arch i386

But the Makefile doesn't use them. As a consequence, it always builds for the compiler's default architecture, not the one we requested, e.g.:

$ port -v installed ipv6calc
The following ports are currently installed:
  ipv6calc @1.0.0_0+universal (active) platform='darwin 16' archs='i386 x86_64' date='2017-10-28T07:47:47-0500'
$ /usr/bin/file $(port -q contents ipv6calc | grep /bin/)
/opt/local/bin/ipv6calc:     Mach-O 64-bit executable x86_64
/opt/local/bin/ipv6loganon:  Mach-O 64-bit executable x86_64
/opt/local/bin/ipv6logconv:  Mach-O 64-bit executable x86_64
/opt/local/bin/ipv6logstats: Mach-O 64-bit executable x86_64