OSXの環境で、gemのpgをインストールする

問題

Can't find the 'libpq-fe.h header
ヘッダーがないためposgresqlのライブラリ(NativeExtension)がコンパイルできずに、失敗した。

$ Gemfile

gem 'pg'

コマンド

$ ./bin/bundle install --path vendor/bundle

出力結果

Gem::Ext::BuildError: ERROR: Failed to build gem native extension.

    /Users/saicologic/.rbenv/versions/2.1.6/bin/ruby extconf.rb
checking for pg_config... no
No pg_config... trying anyway. If building fails, please try again with
 --with-pg-config=/path/to/pg_config
checking for libpq-fe.h... no
Can't find the 'libpq-fe.h header
*** 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
    --without-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=/Users/saicologic/.rbenv/versions/2.1.6/bin/ruby
    --with-pg
    --without-pg
    --enable-windows-cross
    --disable-windows-cross
    --with-pg-config
    --without-pg-config
    --with-pg_config
    --without-pg_config
    --with-pg-dir
    --without-pg-dir
    --with-pg-include
    --without-pg-include=${pg-dir}/include
    --with-pg-lib
    --without-pg-lib=${pg-dir}/lib

extconf failed, exit code 1

解決

Install posgresql

$ brew install postgresql

出力結果

==> Downloading https://homebrew.bintray.com/bottles/postgresql-9.4.1_1.yosemite.bottle.tar.gz
######################################################################## 100.0%
==> Pouring postgresql-9.4.1_1.yosemite.bottle.tar.gz
==> Caveats
If builds of PostgreSQL 9 are failing and you have version 8.x installed,
you may need to remove the previous version first. See:
  https://github.com/Homebrew/homebrew/issues/2510

To migrate existing data from a previous major version (pre-9.4) of PostgreSQL, see:
  https://www.postgresql.org/docs/9.4/static/upgrading.html

To have launchd start postgresql at login:
    ln -sfv /usr/local/opt/postgresql/*.plist ~/Library/LaunchAgents
Then to load postgresql now:
    launchctl load ~/Library/LaunchAgents/homebrew.mxcl.postgresql.plist
Or, if you don't want/need launchctl, you can just run:
    postgres -D /usr/local/var/postgres
==> /usr/local/Cellar/postgresql/9.4.1_1/bin/initdb /usr/local/var/postgres
==> Summary