Reduce the number of times we build a host copy of python.

ports/python-host/nacl.patch

 diff --git a/Include/datetime.h b/Include/datetime.h
 index c0e7ffd..b6d6036 100644
 --- a/Include/datetime.h
 +++ b/Include/datetime.h
 @@ -166,6 +166,8 @@ typedef struct {
  
  #ifdef Py_BUILD_CORE
  
 +#define PyDataTime_STATIC 1
 +
@@ skipping 441 matching lines @@
      if test -z "$PYTHON_FOR_BUILD"; then
 -        for interp in python$PACKAGE_VERSION python2 python; do
 -           which $interp >/dev/null 2>&1 || continue
 -           if $interp -c 'import sys;sys.exit(not (sys.version_info[:2] >= (2,7) and sys.version_info[0] < 3))'; then
 -               break
 -           fi
 -            interp=
 -       done
 +       case "$host" in
 +       *-*-nacl*)
-+           interp=$(cd ../build-nacl-host && pwd)/python.exe
-+           if [ ! -f $interp ]; then interp=$(cd ../build-nacl-host && pwd)/python; fi
++           interp=$(cd ../build_host && pwd)/python.exe
++           if [ ! -f $interp ]; then interp=$(cd ../build_host && pwd)/python; fi
 +           ;;
 +       *)
 +           for interp in python$PACKAGE_VERSION python2 python; do
 +               which $interp >/dev/null 2>&1 || continue
 +               if $interp -c 'import sys;sys.exit(not (sys.version_info@<:@:2@:>@ >= (2,7) and sys.version_info@<:@0@:>@ < 3))'; then
 +                   break
 +               fi
 +               interp=
 +           done
 +           ;;
@@ skipping 71 matching lines @@
      if test -z "$PYTHON_FOR_BUILD"; then
 -        for interp in python$PACKAGE_VERSION python2 python; do
 -           which $interp >/dev/null 2>&1 || continue
 -           if $interp -c 'import sys;sys.exit(not (sys.version_info@<:@:2@:>@ >= (2,7) and sys.version_info@<:@0@:>@ < 3))'; then
 -               break
 -           fi
 -            interp=
 -       done
 +       case "$host" in
 +       *-*-nacl*)
-+           interp=$(cd ../build-nacl-host && pwd)/python
++           interp=$(cd ../build_host && pwd)/python
 +           ;;
 +       *)
 +           for interp in python$PACKAGE_VERSION python2 python; do
 +               which $interp >/dev/null 2>&1 || continue
 +               if $interp -c 'import sys;sys.exit(not (sys.version_info@<:@:2@:>@ >= (2,7) and sys.version_info@<:@0@:>@ < 3))'; then
 +                   break
 +               fi
 +               interp=
 +           done
 +           ;;
@@ skipping 68 matching lines @@
                      version = line.split()[2]
                      break
              if version >= version_req:
 -                if (self.compiler.find_library_file(lib_dirs, 'z')):
 +                # Unconditionally try to link zlib.
 +                # Changing the library path seems to provoke other issues.
 +                if True or (self.compiler.find_library_file(lib_dirs, 'z')):
                      if host_platform == "darwin":
                          zlib_extra_link_args = ('-Wl,-search_paths_first',)
                      else: