无法安装posix-spawn

Question

我通过Xcode > Preferences > Downloads > Components > Command Line Tools安装了Xcode4.6.2命令行工具，它的状态是“已安装”，但是在MacOS10.8.3上重启我的mac后，我没有/Developer文件夹，当我尝试运行sudo gem install posix-spawn时，我得到了这个错误：

Building native extensions.  This could take a while...
ERROR:  Error installing posix-spawn:
    ERROR: Failed to build gem native extension.

/System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/bin/ruby extconf.rb
creating Makefile

make
xcrun cc -I. -I/System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/1.8/universal-darwin12.0 -I/System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/1.8/universal-darwin12.0 -I. -D_XOPEN_SOURCE -D_DARWIN_C_SOURCE   -fno-common -arch i386 -arch x86_64 -g -Os -pipe -fno-common -DENABLE_DTRACE  -fno-common  -pipe -fno-common  -Wall   -c posix-spawn.c
xcrun: Error: could not stat active Xcode path '/Developer'. (No such file or directory)
cc -arch i386 -arch x86_64 -pipe -bundle -undefined dynamic_lookup -o posix_spawn_ext.bundle posix-spawn.o -L. -L/System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib -L. -arch i386 -arch x86_64     -lruby  -lpthread -ldl -lobjc
clang: error: no such file or directory: 'posix-spawn.o'
make: *** [posix_spawn_ext.bundle] Error 1


Gem files will remain installed in /Library/Ruby/Gems/1.8/gems/posix-spawn-0.3.6 for inspection.
Results logged to /Library/Ruby/Gems/1.8/gems/posix-spawn-0.3.6/ext/gem_make.out

other questions建议安装Xcode命令行工具，但我已经这样做了。/usr/bin/gcc-4.2存在。

Answer 1

解决方案是先运行sudo xcode-select -switch /Applications/Xcode.app/Contents/Developer/，然后运行sudo gem install posix-spawn。

Answer 2

重新安装Xcode对我来说很有效。运行xcode-select --install，然后使用gem install posix-spawn安装gem。