Convert has_lib.sh to sh so it also works on BSD OSes

Passes http://www.shellcheck.net/

Ref. #754

util/has_lib.sh

@@ -1,26 +1,27 @@
-#!/bin/bash
+#!/bin/sh
 
 has_ldconfig() {
   hash ldconfig 2>/dev/null
 }
 
 has_system_lib() {
-  local regex="lib$1.+(so|dylib)"
+  regex="lib$1.+(so|dylib)"
 
   # Add /sbin to path as ldconfig is located there on some systems - e.g. Debian
   # (and it still can be used by unprivileged users):
   PATH="$PATH:/sbin"
   export PATH
-  # Try using ldconfig on linux systems
-  if $(has_ldconfig); then
+
+  # Try using ldconfig on Linux systems
+  if has_ldconfig; then
     for _ in $(ldconfig -p 2>/dev/null | grep -E "$regex"); do
       return 0
     done
   fi
 
   # Try just checking common library locations
   for dir in /lib /usr/lib /usr/local/lib /opt/local/lib /usr/lib/x86_64-linux-gnu /usr/lib/i386-linux-gnu; do
-    test -d $dir && ls $dir | grep -E "$regex" && return 0
+    test -d "$dir" && echo "$dir"/* | grep -E "$regex" && return 0
   done
 
   return 1
@@ -52,7 +53,7 @@ case "$1" in
     result=$?
     ;;
   *)
-    >&2 echo "Unknown library: $1"
+    echo "Unknown library: $1"
     exit 1
 esac