p5-net-libidn: use ${configure.cc}

[ryandesign (Ryan Carsten Schmidt)]

p5-net-libidn uses "cc" during the configure phase, causing the following error when the script mentioned in UsingTheRightCompiler is used:

--->  Configuring p5-net-libidn
DEBUG: Using compiler 'Mac OS X gcc 4.0'
DEBUG: Executing org.macports.configure (p5-net-libidn)
DEBUG: Environment: CFLAGS='-O2' CPPFLAGS='-I/mp/include' CXXFLAGS='-O2' MACOSX_DEPLOYMENT_TARGET='10.4' LIBRARY_PATH='/mp/lib' CPP='/usr/bin/cpp-4.0' CXX='/usr/bin/g++-4.0' F90FLAGS='-O2' LDFLAGS='-L/mp/lib' FCFLAGS='-O2' OBJC='/usr/bin/gcc-4.0' INSTALL='/usr/bin/install -c' C_INCLUDE_PATH='/mp/include' FFLAGS='-O2' OBJCFLAGS='-O2' CC='/usr/bin/gcc-4.0'
DEBUG: Assembled command: 'cd "/mp/var/macports/build/_Users_rschmidt_macports_dports_perl_p5-net-libidn/work/Net-LibIDN-0.10" && /mp/bin/perl Makefile.PL INSTALLDIRS=vendor'
cc -lidn -o __test1 __test1.c
cc: Error: You should be using ${configure.cc}
See http://trac.macports.org/wiki/UsingTheRightCompiler
gcc -lidn -o __test1 __test1.c
gcc: Error: You should be using ${configure.cc}
See http://trac.macports.org/wiki/UsingTheRightCompiler

The attached patch fixes this.

[ryandesign (Ryan Carsten Schmidt)]

Committed in r54248 (maintainer timeout).