simple_spin: fix linker error

simple_spin: fix linker error

For some stupid reason the linker is pulling this in twice, resulting in

/bin/sh ../libtool --tag=CXX   --mode=link g++  -Wall -D__CEPH__ -D_FILE_OFFSET_BITS=64 -D_REENTRANT -D_THREAD_SAFE -rdynamic -Wtype-limits -Wignored-qualifiers -Winit-self -Wpointer-arith -fno-strict-aliasing -Wnon-virtual-dtor -Wno-invalid-offsetof -Wstrict-null-sentinel  -g -Wextra -Wno-missing-field-initializers -Wno-missing-declarations -Wno-unused-parameter -Wl,--as-needed -latomic_ops  -o radosgw_admin radosgw_admin-rgw_fs.o radosgw_admin-rgw_rados.o radosgw_admin-rgw_user.o radosgw_admin-rgw_access.o radosgw_admin-rgw_op.o radosgw_admin-rgw_rest.o radosgw_admin-rgw_rest_os.o radosgw_admin-rgw_rest_s3.o radosgw_admin-rgw_common.o radosgw_admin-rgw_cache.o radosgw_admin-rgw_os.o radosgw_admin-rgw_os_auth.o radosgw_admin-rgw_formats.o radosgw_admin-rgw_log.o rgw_escape.o radosgw_admin-rgw_admin.o librgw.a librados.a -lfcgi -lcurl -lexpat -lpthread -lm -lcrypto++
libcommon.a(libcommon_a-simple_spin.o):(.data+0x8): multiple definition of `foo'
test_trans.o:/home/sage/ceph/src/./common/debug.h:51: first defined here

...which points to some larger linking issue.  However, this fixes it for
now.

Signed-off-by: Sage Weil <sage@newdream.net>