... then be warned that Apple, in their infinite wisdom, have decided that people can do without "/usr/include". Of course, to make your life more interesting, "apr-1-config" still returns "/usr/include/apr-1".
I decided on this workaround: $ ls -l /usr total 16 drwxr-xr-x 5 root wheel 170 Aug 25 07:05 X11 lrwxr-xr-x 1 root wheel 3 Jan 26 02:32 X11R6 -> X11 drwxr-xr-x 1083 root wheel 36822 Jan 26 04:07 bin lrwxr-xr-x 1 root wheel 110 Jan 26 04:17 include -> /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.9.sdk/usr/include drwxr-xr-x 263 root wheel 8942 Jan 26 02:38 lib drwxr-xr-x 166 root wheel 5644 Jan 26 04:07 libexec drwxr-xr-x 7 root wheel 238 Aug 5 2012 llvm-gcc-4.2 drwxrwxr-x 26 root admin 884 Jan 26 02:38 local drwxr-xr-x 244 root wheel 8296 Jan 26 02:38 sbin drwxr-xr-x 46 root wheel 1564 Jan 26 02:38 share drwxr-xr-x 4 root wheel 136 Jan 26 02:25 standalone drwxr-xr-x 3 root wheel 102 Dec 20 2012 tmp -- Brane -- Branko Čibej | Director of Subversion WANdisco // Non-Stop Data e. br...@wandisco.com