julia: use the right compiler

[ryandesign (Ryan Carsten Schmidt)]

julia is hardcoding the use of clang in its Makefiles; it should instead honor the value of configure.compiler specified by MacPorts.

DEBUG: Executing proc-pre-org.macports.destroot-destroot-0
DEBUG: Executing org.macports.destroot (julia)
DEBUG: Environment: 
DEBUG: Assembled command: 'cd "/opt/local/var/macports/build/_Users_rschmidt_macports_dports_lang_julia/julia/work/julia-0.3.1" && /usr/bin/make -w install FC=/opt/local/bin/gfortran-mp-4.8 USE_SYSTEM_LLVM=1 LLVM_CONFIG=llvm-config-mp-3.3 USE_SYSTEM_LIBUNWIND=1 USE_SYSTEM_LIBM=1 USE_SYSTEM_GMP=1 USE_SYSTEM_MPFR=1 USE_SYSTEM_ZLIB=1 USE_SYSTEM_READLINE=1 USE_SYSTEM_PCRE=1 USE_SYSTEM_FFTW=1 USE_SYSTEM_ARPACK=1 USE_SYSTEM_SUITESPARSE=1 DESTDIR=/opt/local/var/macports/build/_Users_rschmidt_macports_dports_lang_julia/julia/work/destroot'
DEBUG: Executing command line:  cd "/opt/local/var/macports/build/_Users_rschmidt_macports_dports_lang_julia/julia/work/julia-0.3.1" && /usr/bin/make -w install FC=/opt/local/bin/gfortran-mp-4.8 USE_SYSTEM_LLVM=1 LLVM_CONFIG=llvm-config-mp-3.3 USE_SYSTEM_LIBUNWIND=1 USE_SYSTEM_LIBM=1 USE_SYSTEM_GMP=1 USE_SYSTEM_MPFR=1 USE_SYSTEM_ZLIB=1 USE_SYSTEM_READLINE=1 USE_SYSTEM_PCRE=1 USE_SYSTEM_FFTW=1 USE_SYSTEM_ARPACK=1 USE_SYSTEM_SUITESPARSE=1 DESTDIR=/opt/local/var/macports/build/_Users_rschmidt_macports_dports_lang_julia/julia/work/destroot 
clang -stdlib=libc++ -mmacosx-version-min=10.7 -dumpmachine
clang: Error: You should be using ${configure.cc}
See https://trac.macports.org/wiki/UsingTheRightCompiler

[seanfarley (Sean Farley)]

Forgot to close this before; fixed in r126069.