Issues/0134 openexr2 shared iex_debug trap

[michaeldsmith]

• adds OpenEXR target link libraries to CMakeLists.txt as recommended by OpenEXR Porting Guide https://openexr.com/en/latest/PortingGuide.html
• fixes undefined symbols issue described in Tiff read error when reading EXR file #134 that seems to occur when building OpenEXR and CTL using shared libraries, -DBUILD_SHARED_LIBS=ON

[ 68%] Building CXX object ctlrender/CMakeFiles/ctlrender.dir/format.cc.o
[ 69%] Building CXX object ctlrender/CMakeFiles/ctlrender.dir/compression.cc.o
[ 70%] Linking CXX executable ctlrender
ld: Undefined symbols:
  half::_eLut, referenced from:
      half::half(float) in exr_file.cc.o
  half::convert(int), referenced from:
      half::half(float) in exr_file.cc.o
  half::_toFloat, referenced from:
      half::operator float() const in libIlmCtlSimd.a[14](CtlSimdStdLibLookupTable.cpp.o)

[ 23%] Building CXX object lib/IlmCtlMath/CMakeFiles/IlmCtlMath.dir/CtlRbfInterpolator.cpp.o
[ 24%] Linking CXX shared library libIlmCtlMath.dylib
Undefined symbols for architecture x86_64:
  "iex_debugTrap()", referenced from:
      double Ctl::CG<double, Ctl::LSSOperator<double, Ctl::CRSOperator<double> >, Ctl::NullLinearOperator>::operator()<std::__1::__wrap_iter<double*>, std::__1::__wrap_iter<double*> >(std::__1::__wrap_iter<double*>, std::__1::__wrap_iter<double*>, std::__1::__wrap_iter<double*>, std::__1::__wrap_iter<double*>) const in CtlRbfInterpolator.cpp.o
  "Iex_2_5::ArgExc::ArgExc(std::__1::basic_stringstream<char, std::__1::char_traits<char>, std::__1::allocator<char> >&)", referenced from:
      double Ctl::CG<double, Ctl::LSSOperator<double, Ctl::CRSOperator<double> >, Ctl::NullLinearOperator>::operator()<std::__1::__wrap_iter<double*>, std::__1::__wrap_iter<double*> >(std::__1::__wrap_iter<double*>, std::__1::__wrap_iter<double*>, std::__1::__wrap_iter<double*>, std::__1::__wrap_iter<double*>) const in CtlRbfInterpolator.cpp.o

[meshula]

I can't comment on the docker facing changes, but the conditionals in the cmakelists.txt files all make sense to me.