* common.mk (build-ext): avoid trying to build dynamic libraries
  if configured --with-static-linked-ext.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@48094 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
Fix PNaCl configure/link errors.

* configure.in (nacl_cv_cpu_nick): fix typo in PNaCl.
  (XCFLAGS) Add -isystem flag to pnacl and nacl-newlib
  (CXX): added

* nacl/GNUmakefile.in (CXX): Added
  (PPROGRAM): Use clang++ instead of clang because libnacl_io
  depends on c++ std lib.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@48095 b2dd03c8-39d4-4d8f-98ff-823fe69b080e