Lintian this time only complains about libnfsidmap-regex being built without fortify:
I: libnfsidmap-regex: hardening-no-fortify-functions [usr/lib/x86_64-linux-gnu/libnfsidmap/regex.so]

But the build log has -D_FORTIFY_SOURCE=2:
/bin/bash ../../libtool  --tag=CC   --mode=compile gcc -DHAVE_CONFIG_H -I. -I../../support/include  -I/usr/include/tirpc -Wdate-time -D_FORTIFY_SOURCE=2 -D_GNU_SOURCE -pipe  -Wall  -Wextra  -Werror=strict-prototypes  -Werror=missing-prototypes  -Werror=missing-declarations  -Werror=format=2  -Werror=undef  -Werror=missing-include-dirs  -Werror=strict-aliasing=2  -Werror=init-self  -Werror=implicit-function-declaration  -Werror=return-type  -Werror=switch  -Werror=overflow  -Werror=parentheses  -Werror=aggregate-return  -Werror=unused-result  -fno-strict-aliasing  -Werror=format-overflow=2 -Werror=int-conversion -Werror=incompatible-pointer-types -Werror=misleading-indentation -Wno-cast-function-type -g -O2 -ffile-prefix-map=/home/ubuntu/git/packages/nfs-utils/nfs-utils=. -flto=auto -ffat-lto-objects -flto=auto -ffat-lto-objects -fstack-protector-strong -Wformat -Werror=format-security -c -o regex.lo regex.c

then
libtool: compile:  gcc -DHAVE_CONFIG_H -I. -I../../support/include -I/usr/include/tirpc -Wdate-time -D_FORTIFY_SOURCE=2 -D_GNU_SOURCE -pipe -Wall -Wextra -Werror=strict-prototypes -Werror=missing-prototypes -Werror=missing-declarations -Werror=format=2 -Werror=undef -Werror=missing-include-dirs -Werror=strict-aliasing=2 -Werror=init-self -Werror=implicit-function-declaration -Werror=return-type -Werror=switch -Werror=overflow -Werror=parentheses -Werror=aggregate-return -Werror=unused-result -fno-strict-aliasing -Werror=format-overflow=2 -Werror=int-conversion -Werror=incompatible-pointer-types -Werror=misleading-indentation -Wno-cast-function-type -g -O2 -ffile-prefix-map=/home/ubuntu/git/packages/nfs-utils/nfs-utils=. -flto=auto -ffat-lto-objects -flto=auto -ffat-lto-objects -fstack-protector-strong -Wformat -Werror=format-security -c regex.c  -fPIC -DPIC -o .libs/regex.o

and
libtool: compile:  gcc -DHAVE_CONFIG_H -I. -I../../support/include -I/usr/include/tirpc -Wdate-time -D_FORTIFY_SOURCE=2 -D_GNU_SOURCE -pipe -Wall -Wextra -Werror=strict-prototypes -Werror=missing-prototypes -Werror=missing-declarations -Werror=format=2 -Werror=undef -Werror=missing-include-dirs -Werror=strict-aliasing=2 -Werror=init-self -Werror=implicit-function-declaration -Werror=return-type -Werror=switch -Werror=overflow -Werror=parentheses -Werror=aggregate-return -Werror=unused-result -fno-strict-aliasing -Werror=format-overflow=2 -Werror=int-conversion -Werror=incompatible-pointer-types -Werror=misleading-indentation -Wno-cast-function-type -g -O2 -ffile-prefix-map=/home/ubuntu/git/packages/nfs-utils/nfs-utils=. -flto=auto -ffat-lto-objects -flto=auto -ffat-lto-objects -fstack-protector-strong -Wformat -Werror=format-security -c regex.c -o regex.o >/dev/null 2>&1

But not in the linker state (expected I think):/bin/bash ../../libtool  --tag=CC   --mode=link gcc -pipe  -Wall  -Wextra  -Werror=strict-prototypes  -Werror=missing-prototypes  -Werror=missing-declarations  -Werror=format=2  -Werror=undef  -Werror=missing-include-dirs  -Werror=strict-aliasing=2  -Werror=init-self  -Werror=implicit-function-declaration  -Werror=return-type  -Werror=switch  -Werror=overflow  -Werror=parentheses  -Werror=aggregate-return  -Werror=unused-result  -fno-strict-aliasing  -Werror=format-overflow=2 -Werror=int-conversion -Werror=incompatible-pointer-types -Werror=misleading-indentation -Wno-cast-function-type -g -O2 -ffile-prefix-map=/home/ubuntu/git/packages/nfs-utils/nfs-utils=. -flto=auto -ffat-lto-objects -flto=auto -ffat-lto-objects -fstack-protector-strong -Wformat -Werror=format-security -module -avoid-version -Wl,-Bsymbolic-functions -flto=auto -ffat-lto-objects -flto=auto -Wl,-z,relro -Wl,-z,now -o regex.la -rpath /usr/lib/x86_64-linux-gnu/libnfsidmap regex.lo ../../support/nfs/libnfsconf.la -lresolv

So maybe it's a false alert.