Fixed building on armv7 by disabling neon support in configure. This has no effect on amd64. I tested a build there and all tests passed. 16 tests failed on armv7, all unable to allocate lzma memory if I remember correctly.
Index: Makefile =================================================================== RCS file: /cvs/ports/security/botan2/Makefile,v retrieving revision 1.16 diff -u -p -r1.16 Makefile --- Makefile 12 Apr 2018 09:53:54 -0000 1.16 +++ Makefile 30 Apr 2018 07:28:24 -0000 @@ -39,6 +39,7 @@ CONFIGURE_ARGS = --with-build-dir=${WRKB --prefix=${PREFIX} \ --distribution-info="`uname -sr`" \ --mandir=${PREFIX}/man \ + --disable-neon \ --with-bzip2 \ --with-lzma \ --with-openssl \