Bug detecting incorrect arch for 10.13

[gaming-hacker (G Alexander)]

Hello,

I am building imagemagick for osx 10.13 and only build for x86_64 so in the macports.conf I have specified

build_arch          	x86_64
universal_archs     	x86_64 x86_64

in the variants.conf I have specified

-universal

This macports should now build for x86_64 to my understanding. But here is part of the log file;

version:1
:debug:main Starting logging for ImageMagick 
:debug:sysinfo macOS 10.13.6 (darwin/17.7.0) arch i386
:debug:sysinfo MacPorts 2.7.1
:debug:sysinfo Xcode 9.3.1
:debug:sysinfo SDK 10.13
:debug:sysinfo MACOSX_DEPLOYMENT_TARGET: 10.13

as can be seen somehow macports is picking up i386 initially while later on in the build

:info:build libtool: compile:  /usr/bin/clang++ -DHAVE_CONFIG_H -I. -I./config
-I. -I. -I./Magick++/lib -I/opt/local/include -DMAGICKCORE_HDRI_ENABLE=1 
-DMAGICKCORE_QUANTUM_DEPTH=64 -pipe -Os -stdlib=libc++ -arch x86_64 -pthread
 -MT Magick++/lib/libMagick___7_Q64HDRI_la-Montage.lo -MD -MP -MF 
Magick++/lib/.deps/libMagick___7_Q64HDRI_la-Montage.Tpo 
-c Magick++/lib/Montage.cpp -o Magick++/lib/libMagick___7_Q64HDRI_la-Montage.o >/dev/null 

It is clearly building x86_64.

Now the build finally bombs on opencl

:info:build Undefined symbols for architecture x86_64:
:info:build   "_clBuildProgram", referenced from:
:info:build       _InitializeOpenCL in libMagickCore_7_Q64HDRI_la-opencl.o
:info:build   "_clCreateBuffer", referenced from:
:info:build       _InitializeOpenCL in libMagickCore_7_Q64HDRI_la-opencl.o
:info:build   "_clCreateCommandQueue", referenced from:
:info:build       _InitializeOpenCL in libMagickCore_7_Q64HDRI_la-opencl.o

How to disable or otherwise force macports here to accept x86_64 builds and no i386 build without updating to 10.14? I have successfully built ffmpeg with opencl so I know that opencl x86_64 is not broken.

:debug:sysinfo macOS 10.13.6 (darwin/17.7.0) arch i386