title: libpq-fe.h not found when running rake
body: <p>I'm currently having an issue raking a swift postgresql git submodule. The error is as follows: </p>
  
  <pre><code> $ rake                                                                                                                                                                                                                        
  
      [19:38:19]
  checking for uuid/uuid.h in /usr/include/uuid,/usr/include/postgresql,/usr/local/include/postgresql,/opt/local/include,/opt/local/include/postgresql90,/opt/local/include/postgresql85,/opt/local/include/postgresql84,/sw/include... yes
  checking for libpq-fe.h in /usr/include/postgresql,/usr/local/include/postgresql,/opt/local/include,/opt/local/include/postgresql90,/opt/local/include/postgresql85,/opt/local/include/postgresql84,/sw/include... no
  checking for main() in -luuid... yes
  checking for main() in -lpq... yes
  creating Makefile
  compiling adapter.c
  compiling common.c
  In file included from adapter.c:6:
  In file included from ./adapter.h:7:
  ./common.h:11:10: fatal error: 'libpq-fe.h' file not found
  #include &lt;libpq-fe.h&gt;
           ^
  In file included from common.c:5:
  ./common.h:11:10: fatal error: 'libpq-fe.h' file not found
  #include &lt;libpq-fe.h&gt;
           ^
  1 error generated.
  make: *** [common.o] Error 1
  make: *** Waiting for unfinished jobs....
  1 error generated.
  make: *** [adapter.o] Error 1
  rake aborted!
  unable to compile postgres
  /Users/Dan/Dropbox/My Documents/Programming/Mash/mash-ios/swift-db-postgres/Rakefile:33:in `block (2 levels) in &lt;top (required)&gt;'
  /Users/Dan/Dropbox/My Documents/Programming/Mash/mash-ios/swift-db-postgres/Rakefile:32:in `chdir'
  /Users/Dan/Dropbox/My Documents/Programming/Mash/mash-ios/swift-db-postgres/Rakefile:32:in `block in &lt;top (required)&gt;'
  Tasks: TOP =&gt; default =&gt; test =&gt; compile
  (See full trace by running task with --trace)
  </code></pre>
  
  <p>I have checked that the file does exist at /usr/local/include/libpq-fe.h, and have tried including this in my build path, but the error persists. Uninstalling and reinstalling postgres has no effect. I'm thinking it may have to do with symlinks somewhere along the line, but have no idea how to tackle the issue. Can anyone help me out? Thanks!</p>