Odd whine from grep in www/chromium?

It doesn't seem to cause a real "problem," but... it doesn't look
quite ideal, either:

E.g.:
g1-48(12.2-S)[1] cd /usr/ports/www/chromium/
g1-48(12.2-S)[2] make showconfig
make: "/common/ports/www/chromium/Makefile" line 210: warning: "/usr/bin/grep mempcpy /usr/include/string.h" returned non-zero status
===> The following configuration options are available for chromium-92.0.4515.159_1:
     CODECS=on: Compile and enable patented codecs like H.264
     CUPS=on: CUPS printing system support
     DEBUG=off: Build with debugging support
     DRIVER=on: Install chromedriver
     KERBEROS=on: Kerberos support
     LTO=off: Use Link-Time Optimization
     TEST=off: Build and/or run tests
====> Options available for the group AUDIO
     ALSA=on: ALSA audio architecture support
     PULSEAUDIO=off: PulseAudio sound server support
     SNDIO=off: Sndio audio support
====> Kerberos support: you can only select none or one of them
     HEIMDAL=off: Heimdal Kerberos (security/heimdal)
     HEIMDAL_BASE=off: Heimdal Kerberos (base)
     MIT=off: MIT Kerberos (security/krb5)
===> Use 'make config' to modify these settings
g1-48(12.2-S)[3] 

(I see the message several times when working with ports -- e.g., during
"portmaster -Fa" or "portmaster -da", as well as just after building the
port successfully:

...
      For more information, and contact details about the security
      status of this software, see the following webpage: 
https://www.chromium.org/Home

make: "/common/ports/www/chromium/Makefile" line 210: warning: "/usr/bin/grep mempcpy /usr/include/string.h" returned non-zero status
make: "/common/ports/www/chromium/Makefile" line 210: warning: "/usr/bin/grep mempcpy /usr/include/string.h" returned non-zero status
===>>> Upgrade of chromium-92.0.4515.159 to chromium-92.0.4515.159_1 succeeded

===>>> Returning to update check of installed ports

===>>> Update check of installed ports complete

===>>> The following actions were performed:
        Upgrade of chromium-92.0.4515.159 to chromium-92.0.4515.159_1

)

Environment:
g1-48(12.2-S)[3] uname -aUK
FreeBSD g1-48.catwhisker.org 12.2-STABLE FreeBSD 12.2-STABLE #1108 stable/12-n233711-e99900847a5: Thu Sep  2 03:31:49 PDT 2021     root@g1-48.catwhisker.org:/common/S1/obj/usr/src/amd64.amd64/sys/CANARY  amd64 1202508 1202508

g1-48(12.2-S)[5] gen_fbsd_git_tag -fr /usr/ports .
main-n556810-ea698cc7edbb

Peace,
david
-- 
David H. Wolfskill                              david@catwhisker.org
Life is not intended to be a zero-sum game.

See https://www.catwhisker.org/~david/publickey.gpg for my public key.