Build failure on osx if hevea is installed.

[dbuenzli]

Installing omake when hevea is also installed makes the build fail on osx. opam remove hevea && opam install omake && opam install hevea is a workaround.

#=== ERROR while installing omake.0.10.2 ======================================#
# opam-version 1.2.2
# os           darwin
# command      make
# path         /Users/dbuenzli/.opam/4.03.0/build/omake.0.10.2
# compiler     4.03.0
# exit-code    2
# env-file     /Users/dbuenzli/.opam/4.03.0/build/omake.0.10.2/omake-82586-d2c37b.env
# stdout-file  /Users/dbuenzli/.opam/4.03.0/build/omake.0.10.2/omake-82586-d2c37b.out
# stderr-file  /Users/dbuenzli/.opam/4.03.0/build/omake.0.10.2/omake-82586-d2c37b.err
### stdout ###
# [...]
# --- Checking for strings.h... (found)
# --- Checking for function snprintf... (found)
# --- Checking for optimal filesystem case-sensitivity test... (Mac OS X implementation, using getattrlist)
# --- Checking for function posix_spawn... (found)
# --- Checking for function moncontrol... (found)
# --- Checking if ocamldep understands -modules... (yes)
# --- Checking for hevea... (found /Users/dbuenzli/.opam/4.03.0/bin/hevea)
# --- Checking for hacha... (found /Users/dbuenzli/.opam/4.03.0/bin/hacha)
# --- Checking for hevea configs and version... (2.29 in /Users/dbuenzli/.opam/4.03.0/lib/hevea)
# --- Checking if /Users/dbuenzli/.opam/4.03.0/lib/hevea exists... (yes)
### stderr ###
# /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/ranlib: file: clib.a(c_fam_win32.o) has no symbols
# /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/ranlib: file: clib.a(c_fam_kqueue.o) has no symbols
# /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/ranlib: file: clib.a(c_fam_inotify.o) has no symbols
# Updating the .config file.
# *** omake error:
#    File doc/OMakefile: line 217, characters 4-18
#    directory does not exist: /Users/dbuenzli/.opam/4.03.0/build/omake.0.10.2/doc/html
# Command exited with error: boot/omake '--dotomake' '.omake' '--force-dotomake' 'main' 'OCAML=ocaml'
# make: *** [bootstrap] Error 1

[dbuenzli]

Duplicate of #88.