compile error

===> Compiling c:/Users/olivermt/Documents/code/prototyping/deps/iconv/c_src/iconv.c
===> Microsoft (R) C/C++ Optimizing Compiler Version 19.00.23918 for x64
Copyright (C) Microsoft Corporation.  All rights reserved.

cl : Command line warning D9002 : ignoring unknown option '-g'
iconv.c
c:\program files\erl7.2.1\erts-7.2.1\include\erl_drv_nif.h(40): warning C4820: '<unnamed-tag>': '4' bytes padding added after data member 'dirty_scheduler_support'
c:\Program Files\erl7.2.1\erts-7.2.1\include\erl_nif.h(134): warning C4820: '<unnamed-tag>': '4' bytes padding added after data member 'arity'
c:\Program Files\erl7.2.1\erts-7.2.1\include\erl_nif.h(136): warning C4820: '<unnamed-tag>': '4' bytes padding added after data member 'flags'
c:\Program Files\erl7.2.1\erts-7.2.1\include\erl_nif.h(145): warning C4820: 'enif_entry_t': '4' bytes padding added after data member 'num_of_funcs'
c:\Program Files\erl7.2.1\erts-7.2.1\include\erl_nif.h(152): warning C4820: 'enif_entry_t': '4' bytes padding added after data member 'options'
c:/Users/olivermt/Documents/code/prototyping/deps/iconv/c_src/iconv.c(20): fatal error C1083: Cannot open include file: 'iconv.h': No such file or directory

** (Mix) Could not compile dependency :iconv, "escript.exe "c:/Users/olivermt/.mix/rebar3" bare compile --paths "c:/Users/olivermt/Documents/code/prototyping/_build/dev/lib/*/ebin"" command failed. You can recompile this dependency with "mix deps.compile iconv", update it with "mix deps.update iconv" or clean it with "mix deps.clean iconv"