Installation of jekyll on macOS Sierra fails - ruby

Question

I'm trying to install jekyll on macOS with following versions and xcode command line tools installed with ruby 2.4.0p0 and gem 2.6.10
installing jekyll and bundler
gem install jekyll bundler
the result of the command is
Fetching: public_suffix-2.0.5.gem (100%)
Successfully installed public_suffix-2.0.5
Fetching: addressable-2.5.0.gem (100%)
Successfully installed addressable-2.5.0
Fetching: colorator-1.1.0.gem (100%)
Successfully installed colorator-1.1.0
Fetching: sass-3.4.23.gem (100%)
Successfully installed sass-3.4.23
Fetching: jekyll-sass-converter-1.5.0.gem (100%)
Successfully installed jekyll-sass-converter-1.5.0
Fetching: rb-fsevent-0.9.8.gem (100%)
Successfully installed rb-fsevent-0.9.8
Fetching: ffi-1.9.17.gem (100%)
Building native extensions. This could take a while...
ERROR: Error installing jekyll:
ERROR: Failed to build gem native extension.
current directory: /usr/local/lib/ruby/gems/2.4.0/gems/ffi-1.9.17/ext/ffi_c
/usr/local/opt/ruby/bin/ruby -r ./siteconf20170303-1307-1slrb61.rb extconf.rb
checking for ffi.h... *** extconf.rb failed ***
Could not create Makefile due to some reason, probably lack of necessary
libraries and/or headers. Check the mkmf.log file for more details. You may
need configuration options.
Provided configuration options:
--with-opt-dir
--with-opt-include
--without-opt-include=${opt-dir}/include
--with-opt-lib
--without-opt-lib=${opt-dir}/lib
--with-make-prog
--without-make-prog
--srcdir=.
--curdir
--ruby=/usr/local/Cellar/ruby/2.4.0/bin/$(RUBY_BASE_NAME)
--with-ffi_c-dir
--without-ffi_c-dir
--with-ffi_c-include
--without-ffi_c-include=${ffi_c-dir}/include
--with-ffi_c-lib
--without-ffi_c-lib=${ffi_c-dir}/lib
--with-libffi-config
--without-libffi-config
--with-pkg-config
--without-pkg-config
/usr/local/Cellar/ruby/2.4.0/lib/ruby/2.4.0/mkmf.rb:457:in `try_do': The compiler failed to generate an executable file. (RuntimeError)
You have to install development tools first.
from /usr/local/Cellar/ruby/2.4.0/lib/ruby/2.4.0/mkmf.rb:588:in `try_cpp'
from /usr/local/Cellar/ruby/2.4.0/lib/ruby/2.4.0/mkmf.rb:1095:in `block in have_header'
from /usr/local/Cellar/ruby/2.4.0/lib/ruby/2.4.0/mkmf.rb:945:in `block in checking_for'
from /usr/local/Cellar/ruby/2.4.0/lib/ruby/2.4.0/mkmf.rb:351:in `block (2 levels) in postpone'
from /usr/local/Cellar/ruby/2.4.0/lib/ruby/2.4.0/mkmf.rb:321:in `open'
from /usr/local/Cellar/ruby/2.4.0/lib/ruby/2.4.0/mkmf.rb:351:in `block in postpone'
from /usr/local/Cellar/ruby/2.4.0/lib/ruby/2.4.0/mkmf.rb:321:in `open'
from /usr/local/Cellar/ruby/2.4.0/lib/ruby/2.4.0/mkmf.rb:347:in `postpone'
from /usr/local/Cellar/ruby/2.4.0/lib/ruby/2.4.0/mkmf.rb:944:in `checking_for'
from /usr/local/Cellar/ruby/2.4.0/lib/ruby/2.4.0/mkmf.rb:1094:in `have_header'
from extconf.rb:16:in `<main>'
To see why this extension failed to compile, please check the mkmf.log which can be found here:
/usr/local/lib/ruby/gems/2.4.0/extensions/x86_64-darwin-16/2.4.0/ffi-1.9.17/mkmf.log
extconf failed, exit code 1
Gem files will remain installed in /usr/local/lib/ruby/gems/2.4.0/gems/ffi-1.9.17 for inspection.
Results logged to /usr/local/lib/ruby/gems/2.4.0/extensions/x86_64-darwin-16/2.4.0/ffi-1.9.17/gem_make.out
Fetching: bundler-1.14.5.gem (100%)
Successfully installed bundler-1.14.5
Parsing documentation for bundler-1.14.5
Installing ri documentation for bundler-1.14.5
Done installing documentation for bundler after 4 seconds
1 gem installed
contents of log file mkmf.log
package configuration for libffi is not found
"clang -o conftest -I/usr/local/Cellar/ruby/2.4.0/include/ruby-2.4.0/x86_64-darwin16 -I/usr/local/Cellar/ruby/2.4.0/include/ruby-2.4.0/ruby/backward -I/usr/local/Cellar/ruby/2.4.0/include/ruby-2.4.0 -I. -I/usr/local/opt/libyaml/include -I/usr/local/opt/openssl/include -I/usr/local/opt/readline/include -D_XOPEN_SOURCE -D_DARWIN_C_SOURCE -D_DARWIN_UNLIMITED_SELECT -D_REENTRANT -O3 -fno-fast-math -ggdb3 -Wall -Wextra -Wno-unused-parameter -Wno-parentheses -Wno-long-long -Wno-missing-field-initializers -Wno-tautological-compare -Wno-parentheses-equality -Wno-constant-logical-operand -Wno-self-assign -Wunused-variable -Wimplicit-int -Wpointer-arith -Wwrite-strings -Wdeclaration-after-statement -Wshorten-64-to-32 -Wimplicit-function-declaration -Wdivision-by-zero -Wdeprecated-declarations -Wextra-tokens -fno-common -pipe conftest.c -L. -L/usr/local/Cellar/ruby/2.4.0/lib -L/usr/local/opt/libyaml/lib -L/usr/local/opt/openssl/lib -L/usr/local/opt/readline/lib -L. -fstack-protector -L/usr/local/lib -L/usr/local/opt/libyaml/lib -L/usr/local/opt/openssl/lib -L/usr/local/opt/readline/lib -lruby.2.4.0 -lpthread -ldl -lobjc "
2017-03-03 09:09 xcodebuild[1311] (FSEvents.framework) FSEventStreamStart: ERROR: FSEvents_connect() => (ipc/send) invalid destination port (268435459)
2017-03-03 09:09 xcodebuild[1311] (FSEvents.framework) FSEventStreamInvalidate(): failed assertion 'streamRef != NULL'
2017-03-03 09:09 xcodebuild[1311] (FSEvents.framework) FSEventStreamRelease(): failed assertion 'streamRef != NULL'
2017-03-03 09:09:01.029 xcodebuild[1311:92957] DVTFilePathFSEvents: Failed to start fs event stream.
sh: line 1: 1313 Abort trap: 6 /Applications/Xcode.app/Contents/Developer/usr/bin/xcodebuild -sdk / -find clang 2> /dev/null
clang: error: unable to find utility "clang", not a developer tool or in PATH
checked program was:
/* begin */
1: #include "ruby.h"
2:
3: int main(int argc, char **argv)
4: {
5: return 0;
6: }
/* end */

Answer 1

i looked for solutions to fix clang: error: unable to find utility "clang", not a developer tool or in PATH
and found out that Xcode couldn't find its own Command Line Tools.
This link fixed it for me.