macOS: Switch ChmodBPF to zsh.

Switch the ChmodBPF script to /bin/zsh since it

- Has known behavior, unlike /bin/sh, which execs whatever
  /private/var/select/sh points to.

- Supports 'read -n 0' and other nice features.

- Is unlikely to be deprecated, since it was made the default shell in
  Catalina[1].

- Exists in older macOS releases, unlike dash[2].

Closes #16826.

[1]https://support.apple.com/en-us/HT208050
[2]https://scriptingosx.com/2020/06/about-bash-zsh-sh-and-dash-in-macos-catalina-and-beyond/

CMakeLists.txt

@@ -3474,6 +3474,7 @@ if(SHELLCHECK_EXECUTABLE)
 		COMMAND shellcheck --external-sources
 			image/stock_icons/svg-to-png.sh
 			packaging/appimage/AppRun
+			"packaging/macosx/ChmodBPF/root/Library/Application Support/Wireshark/ChmodBPF/ChmodBPF"
 			packaging/macosx/osx-app.sh.in
 			packaging/macosx/osx-dmg.sh.in
 			packaging/source/git-export-release.sh.in

packaging/macosx/ChmodBPF/root/Library/Application Support/Wireshark/ChmodBPF/ChmodBPF

@@ -1,4 +1,5 @@
-#! /bin/sh
+#! /bin/zsh
+# shellcheck shell=bash
 
 #
 # Unfortunately, macOS's devfs is based on the old FreeBSD
@@ -27,12 +28,12 @@ if [ "$FORCE_CREATE_BPF_MAX" -gt "$SYSCTL_MAX" ] ; then
 	FORCE_CREATE_BPF_MAX=$SYSCTL_MAX
 fi
 
-syslog -s -l notice "ChmodBPF: Forcing creation and setting permissions for /dev/bpf*"
+syslog -s -l notice "ChmodBPF: Forcing creation and setting permissions for /dev/bpf0-$(( FORCE_CREATE_BPF_MAX - 1))"
 
 CUR_DEV=0
 while [ "$CUR_DEV" -lt "$FORCE_CREATE_BPF_MAX" ] ; do
 	# Try to do the minimum necessary to trigger the next device.
-	: < /dev/bpf$CUR_DEV > /dev/null 2>&1
+	read -r -n 0 < /dev/bpf$CUR_DEV > /dev/null 2>&1
 	CUR_DEV=$(( CUR_DEV + 1 ))
 done