Remove i386 from OSX architectures

[heuermh]

I couldn't build with i386 included in the OSX architectures

$ make osx
CHUCK_STRICT=1 make -C ABSaturator/ osx
clang++ -mmacosx-version-min=10.9 -D__MACOSX_CORE__ -I../chuck/include/ -arch i386 -arch x86_64 -O3 -Werror -c -o ABSaturator.o ABSaturator.cpp
clang++ -mmacosx-version-min=10.9 -D__MACOSX_CORE__ -I../chuck/include/ -arch i386 -arch x86_64 -O3 -Werror -c -o Filters.o Filters.cpp
clang++ -mmacosx-version-min=10.9 -shared -lc++ -arch i386 -arch x86_64 -o ABSaturator.chug ABSaturator.o Filters.o
ld: warning: The i386 architecture is deprecated for macOS (remove from the Xcode build setting: ARCHS)
ld: warning: ignoring file /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/lib/libSystem.tbd, missing required architecture i386 in file /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/lib/libSystem.tbd
ld: warning: ignoring file /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/lib/libc++.tbd, missing required architecture i386 in file /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/lib/libc++.tbd
Undefined symbols for architecture i386:
  "__Unwind_Resume", referenced from:
      _absaturator_ctor in ABSaturator.o
  "operator delete(void*)", referenced from:
      _absaturator_ctor in ABSaturator.o
      _absaturator_dtor in ABSaturator.o
  "operator new(unsigned long)", referenced from:
      _absaturator_ctor in ABSaturator.o
  "___gxx_personality_v0", referenced from:
      _absaturator_ctor in ABSaturator.o
      Dwarf Exception Unwind Info (__eh_frame) in ABSaturator.o
  "___stack_chk_fail", referenced from:
      ABSaturator::ABSaturator(float) in ABSaturator.o
  "___stack_chk_guard", referenced from:
      ABSaturator::ABSaturator(float) in ABSaturator.o
  "_log10f", referenced from:
      _absaturator_setDriveDb in ABSaturator.o
      _absaturator_getDriveDb in ABSaturator.o
  "_pow", referenced from:
      _absaturator_setDriveDb in ABSaturator.o
ld: symbol(s) not found for architecture i386
clang: error: linker command failed with exit code 1 (use -v to see invocation)
make[1]: *** [ABSaturator.chug] Error 1
make: *** [ABSaturator/ABSaturator.chug] Error 2

Is that a valid build target any more?