ENH: force build attempt in SimpleITK external project
ENH: force build attempt in SimpleITK external project

Previously, if building from the top level super-build when a file was
modified in the SimpleITK project, the SimpleITK project would not be
rebuild. This patch removed the time stamp, and runs the build command
for the external project.

richardbeare/SimpleITK,SimpleITK/SimpleITK,richardbeare/SimpleITK,InsightSoftwareConsortium/SimpleITK,InsightSoftwareConsortium/SimpleITK,blowekamp/SimpleITK,SimpleITK/SimpleITK,richardbeare/SimpleITK,SimpleITK/SimpleITK,InsightSoftwareConsortium/SimpleITK,SimpleITK/SimpleITK,kaspermarstal/SimpleElastix,kaspermarstal/SimpleElastix,richardbeare/SimpleITK,blowekamp/SimpleITK,richardbeare/SimpleITK,hendradarwin/SimpleITK,hendradarwin/SimpleITK,InsightSoftwareConsortium/SimpleITK,blowekamp/SimpleITK,hendradarwin/SimpleITK,hendradarwin/SimpleITK,richardbeare/SimpleITK,hendradarwin/SimpleITK,blowekamp/SimpleITK,richardbeare/SimpleITK,kaspermarstal/SimpleElastix,SimpleITK/SimpleITK,InsightSoftwareConsortium/SimpleITK,richardbeare/SimpleITK,kaspermarstal/SimpleElastix,blowekamp/SimpleITK,kaspermarstal/SimpleElastix,blowekamp/SimpleITK,InsightSoftwareConsortium/SimpleITK,SimpleITK/SimpleITK,InsightSoftwareConsortium/SimpleITK,hendradarwin/SimpleITK,blowekamp/SimpleITK,hendradarwin/SimpleITK,blowekamp/SimpleITK,SimpleITK/SimpleITK,kaspermarstal/SimpleElastix,hendradarwin/SimpleITK,kaspermarstal/SimpleElastix,SimpleITK/SimpleITK,InsightSoftwareConsortium/SimpleITK