BUG: Do not ENABLED_SHARED for GDCMIO

With shared libraries on windows and export specification with gcc,
memory leaking is being detected by valgrind. This should be
re-enabled when GDCM it self is enabled as shared with export
specifications.

Change-Id: Ib28f1e98cc66cd9cb4e28f935934290560fb99c9
Merge topic 'GDCMNoENABLED_SHARED'

30aca620 BUG: Do not ENABLED_SHARED for GDCMIO