jemalloc: remove symbol prefix on darwin

The default darwin build added a je_ prefix to all exported symbols, and
that broke downstream consumers that were not expecting the prefix, like
mariadb.

pkgs/development/libraries/jemalloc/default.nix

@@ -8,6 +8,11 @@ stdenv.mkDerivation rec {
     sha256 = "1bmdr51wxiir595k2r6z9a7rcgm42kkgnr586xir7vdcndr3pwf8";
   };
 
+  # By default, jemalloc puts a je_ prefix onto all its symbols on OSX, which
+  # then stops downstream builds (mariadb in particular) from detecting it. This
+  # option should remove the prefix and give us a working jemalloc.
+  configureFlags = stdenv.lib.optional stdenv.isDarwin "--with-jemalloc-prefix=";
+
   meta = with stdenv.lib; {
     homepage = http://www.canonware.com/jemalloc/index.html;
     description = "General purpose malloc(3) implementation";