Fix detection of "std" flag in CMAKE_CXX_FLAGS
Fix detection of "std" flag in CMAKE_CXX_FLAGS

re-ordered the loop so that the "std" flag did not have to be the last
one to be detected.

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