Don't corrupt the thread list in static executables.

Several previous changes conspired to make a mess of the thread list
in static binaries. This was most obvious when trying to call
pthread_key_delete(3) on the main thread.

Bug: http://code.google.com/p/android/issues/detail?id=36893
Change-Id: I2a2f553114d8fb40533c481252b410c10656da2e