OSX makefile fix and install instructions

[bjarthur]

addresses #138

and adds more detail to README

[ihnorton]

Thanks, just so I understand: is the stdlib change necessary because Homebrew Julia and llvm are built with gcc? (I don't have a mac to check this myself at the moment)

[yuyichao]

Is this linking against both libc++ and libstdc++?

[bjarthur]

i don't know whether this change is needed b/c of gcc or not. just know that it works. perhaps @btello can say.

moreover both -libstdc++ and lc++ are needed. removing either one causes the build to fail for different reasons. transcripts follow.

julia> Pkg.build("Clang")
INFO: Building Clang
g++ wrapclang.cpp.o -rdynamic -shared -o libwrapclang.dylib -L/usr/local/Cellar/llvm/3.6.2/lib  -L/usr/local/Cellar/llvm/3.6.2/lib -lclang -stdlib=libstdc++
Undefined symbols for architecture x86_64:
  "std::__1::__vector_base_common<true>::__throw_length_error() const", referenced from:
      void std::__1::vector<CXCursor, std::__1::allocator<CXCursor> >::__push_back_slow_path<CXCursor const>(CXCursor const&) in wrapclang.cpp.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)
make: *** [libwrapclang.dylib] Error 1
================================[ ERROR: Clang ]================================

LoadError: failed process: Process(`make`, ProcessExited(2)) [2]
while loading /Users/arthurb/.julia/v0.4/Clang/deps/build.jl, in expression starting on line 19

================================================================================

================================[ BUILD ERRORS ]================================

WARNING: Clang had build errors.

 - packages with build errors remain installed in /Users/arthurb/.julia/v0.4
 - build the package(s) and all dependencies with `Pkg.build("Clang")`
 - build a single package by running its `deps/build.jl` script

================================================================================

julia> Pkg.build("Clang")
INFO: Building Clang
g++ wrapclang.cpp.o -rdynamic -shared -o libwrapclang.dylib -L/usr/local/Cellar/llvm/3.6.2/lib  -L/usr/local/Cellar/llvm/3.6.2/lib -lclang -lc++
Undefined symbols for architecture x86_64:
  "std::terminate()", referenced from:
      ___clang_call_terminate in wrapclang.cpp.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)
make: *** [libwrapclang.dylib] Error 1
================================[ ERROR: Clang ]================================

LoadError: failed process: Process(`make`, ProcessExited(2)) [2]
while loading /Users/arthurb/.julia/v0.4/Clang/deps/build.jl, in expression starting on line 19

================================================================================

================================[ BUILD ERRORS ]================================

WARNING: Clang had build errors.

 - packages with build errors remain installed in /Users/arthurb/.julia/v0.4
 - build the package(s) and all dependencies with `Pkg.build("Clang")`
 - build a single package by running its `deps/build.jl` script

================================================================================

julia> Pkg.build("Clang")
INFO: Building Clang
g++ wrapclang.cpp.o -rdynamic -shared -o libwrapclang.dylib -L/usr/local/Cellar/llvm/3.6.2/lib  -L/usr/local/Cellar/llvm/3.6.2/lib -lclang -stdlib=libstdc++ -lc++

julia> 

[btello]

Yeah I'm not exactly sure what the reason is that you would need both c++ libraries but this fix appears to do the trick for me as well.

[yuyichao]

Does something like -stdlib=libc++ -lc++abi works? (or a combination of these... ;-p)

[bjarthur]

yes, -stdlib=libc++ -lc++abi works too. is that preferable?

[bjarthur]

bump. is there a reason not to merge this PR? i'm happy to make the change @yuyichao inquired about but am unsure what the difference is.

[ihnorton]

Linking against both C++ standard libraries is not advised. Please try 04aad3a.

[bjarthur]

8fa3cb8 fixes this.