adding "xcode-select --install" to the docs

[isofer]

I had tons of errors when installing on Mac: missing header files, and libraries (see below). All of them got resolved once I run "xcode-select --install". Please consider adding it to README.md, in the 'compiling on mac section'

''' example_apps/connectedcomponents.cpp:47:17: error: cmath: No such file or directory example_apps/connectedcomponents.cpp:48:18: error: string: No such file or directory In file included from example_apps/connectedcomponents.cpp:50: ./src/graphchi_basic_includes.hpp:36:19: error: sstream: No such file or directory In file included from ./src/graphchi_basic_includes.hpp:38, from example_apps/connectedcomponents.cpp:50: ./src/api/chifilenames.hpp:36:19: error: fstream: No such file or directory ./src/api/chifilenames.hpp:43:18: error: vector: No such file or directory In file included from ./src/api/chifilenames.hpp:47, from ./src/graphchi_basic_includes.hpp:38, from example_apps/connectedcomponents.cpp:50: ./src/logger/logger.hpp:53:19: error: cstdlib: No such file or directory ./src/logger/logger.hpp:54:20: error: iostream: No such file or directory ./src/logger/logger.hpp:55:19: error: cassert: No such file or directory ./src/logger/logger.hpp:56:19: error: cstring: No such file or directory ./src/logger/logger.hpp:57:19: error: cstdarg: No such file or directory In file included from ./src/api/graph_objects.hpp:39, from ./src/api/graphchi_program.hpp:35, from ./src/graphchi_basic_includes.hpp:40, from example_apps/connectedcomponents.cpp:50: ./src/util/qsort.hpp:27:21: error: algorithm: No such file or directory In file included from ./src/io/stripedio.hpp:48, from ./src/api/vertex_aggregator.hpp:42, from ./src/graphchi_basic_includes.hpp:43, from example_apps/connectedcomponents.cpp:50: ./src/metrics/metrics.hpp:34:15: error: map: No such file or directory ./src/metrics/metrics.hpp:36:18: error: limits: No such file or directory In file included from ./src/metrics/metrics.hpp:40, from ./src/io/stripedio.hpp:48, from ./src/api/vertex_aggregator.hpp:42, from ./src/graphchi_basic_includes.hpp:43, from example_apps/connectedcomponents.cpp:50: ./src/util/pthread_tools.hpp:15:16: error: list: No such file or directory In file included from ./src/util/cmdopts.hpp:38, from ./src/metrics/metrics.hpp:41, from ./src/io/stripedio.hpp:48, from ./src/api/vertex_aggregator.hpp:42, from ./src/graphchi_basic_includes.hpp:43, from example_apps/connectedcomponents.cpp:50: ./src/util/configfile.hpp:34:18: error: cstdio: No such file or directory In file included from ./src/io/stripedio.hpp:49, from ./src/api/vertex_aggregator.hpp:42, from ./src/graphchi_basic_includes.hpp:43, from example_apps/connectedcomponents.cpp:50: ./src/util/synchronized_queue.hpp:4:17: error: queue: No such file or directory In file included from ./src/api/chifilenames.hpp:47, from ./src/graphchi_basic_includes.hpp:38, from example_apps/connectedcomponents.cpp:50: ./src/logger/logger.hpp:127: error: ‘stringstream’ in namespace ‘std’ does not name a type ./src/logger/logger.hpp:155: error: ‘string’ in namespace ‘std’ does not name a type ./src/logger/logger.hpp:202: error: declaration of ‘operator<<’ as non-function ./src/logger/logger.hpp:202: error: expected ‘;’ before ‘(’ token In file included from ./src/engine/graphchi_engine.hpp:54, from ./src/graphchi_basic_includes.hpp:45, from example_apps/connectedcomponents.cpp:50: ./src/shards/memoryshard.hpp:162: error: expected ;' before end of line ./src/shards/memoryshard.hpp:162: error: expected}' before end of line In file included from ./src/api/chifilenames.hpp:47, from ./src/graphchi_basic_includes.hpp:38, from example_apps/connectedcomponents.cpp:50: ./src/logger/logger.hpp: In member function ‘void file_logger::set_log_to_console(bool)’: ./src/logger/logger.hpp:151: error: ‘log_to_console’ was not declared in this scope ./src/logger/logger.hpp: In member function ‘bool file_logger::get_log_to_console()’: ./src/logger/logger.hpp:161: error: ‘log_to_console’ was not declared in this scope ./src/logger/logger.hpp: In member function ‘int file_logger::get_log_level()’: ./src/logger/logger.hpp:166: error: ‘log_level’ was not declared in this scope ./src/logger/logger.hpp: In member function ‘file_logger& file_logger::operator<<(T)’: ./src/logger/logger.hpp:174: error: ‘streambuffkey’ was not declared in this scope ./src/logger/logger.hpp:176: error: ‘stringstream’ is not a member of ‘std’ ./src/logger/logger.hpp:176: error: ‘streambuffer’ was not declared in this scope ./src/logger/logger.hpp:176: error: ‘struct logger_impl::streambuff_tls_entry’ has no member named ‘streambuffer’ ./src/logger/logger.hpp: In member function ‘file_logger& filelogger::operator<<(const char)’: ./src/logger/logger.hpp:187: error: ‘streambuffkey’ was not declared in this scope ./src/logger/logger.hpp:189: error: ‘stringstream’ is not a member of ‘std’ ./src/logger/logger.hpp:189: error: ‘streambuffer’ was not declared in this scope ./src/logger/logger.hpp:189: error: ‘struct logger_impl::streambuff_tls_entry’ has no member named ‘streambuffer’ ./src/logger/logger.hpp:194: error: ‘strlen’ was not declared in this scope ./src/logger/logger.hpp:195: error: ‘stream_flush’ was not declared in this scope In file included from ./src/engine/graphchi_engine.hpp:54, from ./src/graphchi_basic_includes.hpp:45, from exampleapps/connectedcomponents.cpp:50: ./src/shards/memoryshard.hpp: At global scope: ./src/shards/memoryshard.hpp:162: error: expected unqualified-id before end of line ./src/shards/memoryshard.hpp:162: error: expected declaration before end of line ./src/logger/logger.hpp:119: warning: ‘messages’ defined but not used make: ** [example_apps/connectedcomponents] Error 1 '''

[akyrola]

Thanks for the suggestion! And sorry for getting back to you so late.