This is fine unless we do clone(2) with CLONE_THREAD flag.

…nd MacOSX.

For systems using ldconfig with different syntax (ex, FreeBSD or
MacOSX), we need to fallback LD path to defaults.

Tested on FreeBSD 9.1 with following steps:

 # For dependency
 pkg_add -r wget protobuf protobuf-c v8 openjdk7 boost-all gmake
 pkg_add -r bash node npm py-yaml gcc48
 npm install -g less coffee-script handlebars

 # To build with GCC48:
 CXX=gcc48 ./configure --ccache
 # Edit config.mk to add "ALLOW_WARNINGS := 1"

 # To build with system clang 3.1:
 CXX=clang ./configure --ccache
 # You have to install system libc++ by:
 #  cd /usr/src/lib/libc++; sudo make install
 # Then edit config.mk to add "ALLOW_WARNINGS := 1"

 # To build
 gmake