PDAL fails to build on 10.6.8: Undefined symbols for architecture x86_64: "___cxa_thread_atexit"

[barracuda156]

See: ​https://build.macports.org/builders/ports-10.6_x86_64-builder/builds/159320/steps/install-port/logs/stdio

Undefined symbols for architecture x86_64:
  "___cxa_thread_atexit", referenced from:
      pdal::BOX2D::parse(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&, unsigned long&) in Bounds.cpp.o
      pdal::BOX3D::parse(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&, unsigned long&) in Bounds.cpp.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)