我想boost使用指定的编译器进行安装，例如gcc-4.9.1我在<gcc_49_root>. 当前的操作系统是 Mac OS X 10.9.4，但我希望此安装过程适用于其他操作系统。的文档boost对这种情况非常不透明。我尝试过的内容如下：
$ ./bootstrap.sh
-n Building Boost.Build engine with toolset darwin...
tools/build/src/engine/bin.macosxx86_64/b2
-n Detecting Python version...
2.7
-n Detecting Python root...
/System/Library/Frameworks/Python.framework/Versions/2.7
-n Unicode/ICU support for Boost.Regex?...
not found.
Generating Boost.Build configuration in project-config.jam...
插入using gcc : 4.9.1 : <gcc_49_root>/bin/g++-4.9 : ;到project-config.jam。
$ ./b2 --prefix=<...> toolset=gcc-4.9.1 install
但是遇到了错误：
Jamfile</Users/dongli/Shares/works/packman/test/packages/Boost/boost_1_56_0/libs/context/build>.gas64 bin.v2/libs/context/build/gcc-4.9.1/release/address-model-64/architecture-x86/threading-multi/asm/make_x86_64_sysv_macho_gas.o
FATAL:/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../libexec/as/x86_64/as: I don't understand '-' flag!
clang: error: no input files
cpp -x assembler-with-cpp …