slow execution when shared linking

[jordisayol]

Runtime speed varies a lot for examples/concurrency/ThreadFiberGCStress.d depending is statically or dynamically linked.

Static:

$ $ dmd -I/usr/include/dmd -defaultlib=libphobos2.a -L-l:libtango-dmd.a -L-l:libbz2.a -L-l:libdl.so ThreadFiberGCStress.d
$ time ./ThreadFiberGCStress
...
real    0m0.086s
user    0m0.056s
sys     0m0.020s

Dynamic:

$ dmd -I/usr/include/dmd -defaultlib=libphobos2.so -L-l:libtango-dmd.so -L-l:libbz2.so -L-l:libdl.so ThreadFiberGCStress.d
$ time ./ThreadFiberGCStress
...
real    0m1.823s
user    0m1.588s
sys     0m0.032s