Homebrew wants me to delete /usr/local/lib? From the Homebrew installation page :


  We recommend you delete /usr/local/include and /usr/local/lib


But my /usr/local/lib contains the following files:

$ ls /usr/local/lib
charset.alias                   libgettextsrc.la
gettext                         libgpg-error.0.dylib
libasprintf.0.0.0.dylib         libgpg-error.dylib
libasprintf.0.dylib             libgpg-error.la
libasprintf.dylib               libiconv.2.dylib
libasprintf.la                  libiconv.dylib
libassuan.0.dylib               libiconv.la
libassuan.dylib                 libintl.8.0.2.dylib
libassuan.la                    libintl.8.dylib
libcharset.1.dylib              libintl.dylib
libcharset.dylib                libintl.la
libcharset.la                   libksba.8.9.6.dylib
libgcrypt.11.6.0.dylib          libksba.8.dylib
libgcrypt.11.dylib              libksba.dylib
libgcrypt.dylib                 libksba.la
libgcrypt.la                    libpth.20.0.27.dylib
libgettextlib-0.17.dylib        libpth.20.dylib
libgettextlib.dylib             libpth.dylib
libgettextlib.la                libpth.la
libgettextpo.0.4.0.dylib        libusb-0.1.4.dylib
libgettextpo.0.dylib            libusb-1.0.0.dylib
libgettextpo.dylib              libusb-1.0.dylib
libgettextpo.la                 libusb-1.0.la
libgettextsrc-0.17.dylib        libusb.dylib
libgettextsrc.dylib             libusb.la


What are these files for? Is it safe to delete these files?
That's kinda the problem; Homebrew doesn't know what they are either, and randomly sourced libraries tend to break builds.  (MacPorts makes the same recommendation.  In fact, I was under the impression that was one of the things Homebrew relaxed.)

If you don't know what they are or if they're used, the simplest solution is

$ sudo mv /usr/local /usr/local.keep


and watch to see what breaks.  Chances are they're used by whatever's in /usr/local/bin, though, so look there first.