Would it be possible to add a definition to the file
ITK/Modules/ThirdParty/VNL/src/vxl/vcl/vcl_compiler.h
to support GCC 8.1
It was pretty easy to fix manually, and the build seems to have succeeded with my small hack
+ 89 # elif (__GNUC__==8)
+ 90 # define VCL_GCC_8
+ 91 # if (__GNUC_MINOR__ > 2 )
+ 92 # define VCL_GCC_83
+ 93 # elif (__GNUC_MINOR__ > 1 )
+ 94 # define VCL_GCC_82
+ 95 # elif (__GNUC_MINOR__ > 0 )
+ 96 # define VCL_GCC_81
+ 97 # else
+ 98 # define VCL_GCC_80
+ 99 # endif