Utop not installing

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1 
Yashwanths-MacBook-Pro:~ yashwanthreddy$ opam install lwt
The following actions will be performed:
  βˆ— install lwt 4.3.0

<><> Gathering sources ><><><><><><><><><><><><><><><><><><><><><><><><><><>  🐫 
[lwt.4.3.0] found in cache

<><> Processing actions <><><><><><><><><><><><><><><><><><><><><><><><><><>  🐫 
[ERROR] The compilation of lwt failed at "/Users/yashwanthreddy/.opam/opam-init/hooks/sandbox.sh build dune build -p lwt -j 7".

#=== ERROR while compiling lwt.4.3.0 ==========================================#
# context     2.0.5 | macos/x86_64 | ocaml-system.4.08.1 | https://opam.ocaml.org#852124c0
# path        ~/.opam/default/.opam-switch/build/lwt.4.3.0
# command     ~/.opam/opam-init/hooks/sandbox.sh build dune build -p lwt -j 7
# exit-code   1
# env-file    ~/.opam/log/lwt-50424-ffb3fd.env
# output-file ~/.opam/log/lwt-50424-ffb3fd.out
### output ###
# [...]
# #include <stdlib.h>
#          ^~~~~~~~~~
# 1 error generated.
#       ocamlc src/unix/lwt_libev_stubs.o (exit 2)
# (cd _build/default/src/unix && /usr/local/bin/ocamlc.opt -g -I /Users/yashwanthreddy/.opam/default/lib/bytes -I /Users/yashwanthreddy/.opam/default/lib/mmap -I /Users/yashwanthreddy/.opam/default/lib/ocplib-endian -I /Users/yashwanthreddy/.opam/default/lib/result -I /Users/yashwanthreddy/.opam/default/lib/seq -I /usr/local/lib/ocaml/threads -I ../core -ccopt -I. -ccopt -g -o lwt_libev_stubs.o[...]
# In file included from lwt_libev_stubs.c:9:
# In file included from ./lwt_unix.h:11:
# In file included from /usr/local/lib/ocaml/caml/mlvalues.h:23:
# /usr/local/lib/ocaml/caml/misc.h:29:10: fatal error: 'stdlib.h' file not found
# #include <stdlib.h>
#          ^~~~~~~~~~
# 1 error generated.



<><> Error report <><><><><><><><><><><><><><><><><><><><><><><><><><><><><>  🐫 
β”Œβ”€ The following actions failed
β”‚ Ξ» build lwt 4.3.0
└─ 
╢─ No changes have been performed

<><> lwt.4.3.0 troubleshooting ><><><><><><><><><><><><><><><><><><><><><><>  🐫 
=> Lwt 5.0.0 will make some breaking changes in November 2019. See
     https://github.com/ocsigen/lwt/issues/584
Yashwanths-MacBook-Pro:~ yashwanthreddy$

Please let me know what is the issue.

2

There seem to be a problem with your C environment. What happens if you:

cd /tmp
echo "#include <stdlib.h>" > a.c
opam exec -- cc -c a.c