问题描述：

• 以前已经安装的 rails 都是可以正常运行的，比如用 rvm 安装的 2.2.2，rails 的版本是 4.2.5，正常运行
• 通过 rvm 安装的 ruby 版本，若未安装 rails，则安装 rails 时报错
• 第一次发现这个问题时大约 4 天前，用 rvm 安装了 2.3.0，安装成功后，尝试安装 rails，报错

详细错误：

Running 'configure' for libxml2 2.9.2... ERROR, review '/Users/killernova/.rvm/gems/ruby-2.2.0/gems/nokogiri-1.6.7.1/ext/nokogiri/tmp/x86_64-apple-darwin15/ports/libxml2/2.9.2/configure.log' to see what happened. Last lines are:
========================================================================
: command not foundem type... ./config.guess: line 4:
: command not founde 6:
: command not founde 33:
: command not founde 34:
: command not founde 36:
: command not founde 48:
: command not founde 57:
: command not founde 60:
'/config.guess: line 63: syntax error near unexpected token `in
'/config.guess: line 63: `  case $1 in
configure: error: cannot guess build type; you must specify one
========================================================================
*** extconf.rb failed ***
Could not create Makefile due to some reason, probably lack of necessary
libraries and/or headers.  Check the mkmf.log file for more details.  You may
need configuration options.

Provided configuration options:
    --with-opt-dir
    --without-opt-dir
    --with-opt-include
    --without-opt-include=${opt-dir}/include
    --with-opt-lib
    --without-opt-lib=${opt-dir}/lib
    --with-make-prog
    --without-make-prog
    --srcdir=.
    --curdir
    --ruby=/System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/bin/ruby
    --help
    --clean
    --use-system-libraries
    --enable-static
    --disable-static
    --with-zlib-dir
    --without-zlib-dir
    --with-zlib-include
    --without-zlib-include=${zlib-dir}/include
    --with-zlib-lib
    --without-zlib-lib=${zlib-dir}/lib
    --enable-cross-build
    --disable-cross-build
/Library/Ruby/Gems/2.0.0/gems/mini_portile2-2.0.0/lib/mini_portile2/mini_portile.rb:366:in `block in execute': Failed to complete configure task (RuntimeError)
    from /Library/Ruby/Gems/2.0.0/gems/mini_portile2-2.0.0/lib/mini_portile2/mini_portile.rb:337:in `chdir'
    from /Library/Ruby/Gems/2.0.0/gems/mini_portile2-2.0.0/lib/mini_portile2/mini_portile.rb:337:in `execute'
    from /Library/Ruby/Gems/2.0.0/gems/mini_portile2-2.0.0/lib/mini_portile2/mini_portile.rb:106:in `configure'
    from /Library/Ruby/Gems/2.0.0/gems/mini_portile2-2.0.0/lib/mini_portile2/mini_portile.rb:149:in `cook'
    from extconf.rb:289:in `block (2 levels) in process_recipe'
    from extconf.rb:182:in `block in chdir_for_build'
    from extconf.rb:181:in `chdir'
    from extconf.rb:181:in `chdir_for_build'
    from extconf.rb:288:in `block in process_recipe'
    from extconf.rb:187:in `tap'
    from extconf.rb:187:in `process_recipe'
    from extconf.rb:478:in `<main>'

mkmf.log

"xcrun clang -o conftest -I/System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/include/ruby-2.0.0/universal-darwin15 -I/System/Library/Frame    works/Ruby.framework/Versions/2.0/usr/include/ruby-2.0.0/ruby/backward -I/System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/include/ruby-2.    0.0 -I. -D_XOPEN_SOURCE -D_DARWIN_C_SOURCE -D_DARWIN_UNLIMITED_SELECT -D_REENTRANT    -g -Os -pipe -DHAVE_GCC_SYNC_BUILTINS  conftest.c  -L. -L/Sys    tem/Library/Frameworks/Ruby.framework/Versions/2.0/usr/lib -L. -L/usr/local/lib   -arch x86_64 -arch i386   -lruby.2.0.0 -liconv -lpthread -ldl -lo    bjc  "
 94 checked program was:
 95 /* begin */
 96  1: #include "ruby.h"
 97  2:
 98  3: #include <stdlib.h>
 99  4: #include <iconv.h>
100  5:
101  6: int main(void)
102  7: {
103  8:     iconv_t cd = iconv_open("", "");
104  9:     iconv(cd, NULL, NULL, NULL, NULL);
105 10:     return EXIT_SUCCESS;
106 11: }
107 /* end */

google 搜索出来，一般都是这样说的：

search for /usr/share/automake*/config.guess

check the latest version of automake

$ which automake
$ automake --version
find the appropriate automake folder in /usr/share/automake.1.11.1/config.guess

replace config.guess from your build tree with /usr/share/automake.1.11.1/config.guess

但是我并不能找到这个文件，类似的，找到的是：

/usr/lib/php/build/config.guess
/usr/local/Cellar/automake/1.15/share/automake-1.15/config.guess
/usr/local/Cellar/libtool/2.4.6/share/libtool/build-aux/config.guess

此外，还有说从网上下载 config.guess 和 config.sub 进行替换

假设是这这些 config.guess 中的一个，替换后请问该如何操作？如果不是这些问题引起的，请问到底是什么情况？谢谢。

＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝分割线＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝

问题暂时解决了：

• 报错的时候有提示是gem install nokogiri -- --use-system-libraries, 但不知道为什么我试了一次没用。
• 然后刚我已经有 rails 的 ruby 版本中，新建了一个项目，bundle install 的时候又出现这个提示，我又按提示试了一次，然后就可以继续 bundle 了。
• 于是我切换到 2.3.0 版本的 ruby，gem install rails，照例提示错误，按提示gem install nokogiri -- --use-system-libraries，成功，gem install rails ，竟然成功了。。。

但肯定还是有问题的，每次运行 ｀gem install nokogiri -- --use-system-libraries｀肯定不是办法，所以请各位帮忙看看到底问题出在哪里？