Fix tools/*-setup.sh to work with no arguments

They were checking for --help in an unusual manner that failed when
run with no arguments.

I've checked that --help works for each script, and that debian-setup.sh
actually works.

NOTE: bsd-setup.sh and rpm-setup.sh seem to have sometimes-broken
formatting, because they try to pass escape sequences to echo, which
POSIX says is implementation-defined (except on XSI-conformant systems).

These changes were mostly made using the following script, with a
manual fix in bsd-setup.sh because it isn't using "switch case".

```python
#!/bin/env python3

import sys
import re

usage_p = re.compile(r'^if \[ "\$1" = "--help" \]\nthen\n((?:\t(?:printf|echo) .*\n)*)\texit 1\nfi$',
                     re.MULTILINE)

case_p = re.compile(r'(^\tcase \$arg in$)',
                    re.MULTILINE)

root_check_p = re.compile(r'(\n# Check if the user is root(?:\n|.)*?fi\n)',
                          re.MULTILINE)

done_p = re.compile(r'(^done\n)',
                    re.MULTILINE)

def fix_setup(name: str):
    assert name.endswith('-setup.sh')

    with open(name, 'r') as fin:
        s = fin.read()

    s = usage_p.sub(r'function print_usage() {\n\1}', s)
    s = case_p.sub(r'''\1
\t\t--help)
\t\t\tprint_usage
\t\t\texit 0
\t\t\t;;''', s)

    m1 = root_check_p.search(s)
    if m1:
        root_check = m1[0]
        s = root_check_p.sub('', s)
        pos = done_p.search(s).end()  # type: ignore[union-attr]
        s = s[:pos] + root_check + s[pos:]

    with open(name, 'w') as fout:
        fout.write(s)

if __name__ == '__main__':
    for name in sys.argv[1:]:
        fix_setup(name)
```

tools/alpine-setup.sh

@@ -13,27 +13,22 @@
 
 set -e -u -o pipefail
 
-if [ "$1" = "--help" ]
-then
+function print_usage() {
 	printf "\\nUtility to setup a alpine system for Wireshark Development.\\n"
 	printf "The basic usage installs the needed software\\n\\n"
 	printf "Usage: %s [--install-optional] [--install-deb-deps] [...other options...]\\n" "$0"
 	printf "\\t--install-optional: install optional software as well\\n"
 	printf "\\t[other]: other options are passed as-is to apt\\n"
-	exit 1
-fi
-
-# Check if the user is root
-if [ "$(id -u)" -ne 0 ]
-then
-	echo "You must be root."
-	exit 1
-fi
+}
 
 ADDITIONAL=0
 OPTIONS=
 for arg; do
 	case $arg in
+		--help)
+			print_usage
+			exit 0
+			;;
 		--install-optional)
 			ADDITIONAL=1
 			;;
@@ -43,6 +38,13 @@ for arg; do
 	esac
 done
 
+# Check if the user is root
+if [ "$(id -u)" -ne 0 ]
+then
+	echo "You must be root."
+	exit 1
+fi
+
 BASIC_LIST="cmake \
 	ninja \
 	gcc \

tools/arch-setup.sh

@@ -13,8 +13,7 @@
 
 set -e -u -o pipefail
 
-if [ "$1" = "--help" ]
-then
+function print_usage() {
 	printf "\\nUtility to setup a pacman-based system for Wireshark development.\\n"
 	printf "The basic usage installs the needed software\\n\\n"
 	printf "Usage: %s [--install-optional] [...other options...]\\n" "$0"
@@ -23,15 +22,7 @@ then
 	printf "\\t--install-all: install everything\\n"
 	printf "\\t[other]: other options are passed as-is to pacman\\n"
 	printf "\\tPass --noconfirm to bypass any \"are you sure?\" messages.\\n"
-	exit 1
-fi
-
-# Check if the user is root
-if [ "$(id -u)" -ne 0 ]
-then
-	echo "You must be root."
-	exit 1
-fi
+}
 
 ADDITIONAL=0
 TESTDEPS=0
@@ -39,6 +30,10 @@ AUR=0
 OPTIONS=
 for arg; do
 	case $arg in
+		--help)
+			print_usage
+			exit 0
+			;;
 		--install-optional)
 			ADDITIONAL=1
 			;;
@@ -56,6 +51,13 @@ for arg; do
 	esac
 done
 
+# Check if the user is root
+if [ "$(id -u)" -ne 0 ]
+then
+	echo "You must be root."
+	exit 1
+fi
+
 BASIC_LIST="base-devel \
 	bcg729 \
 	brotli \

tools/bsd-setup.sh

@@ -13,22 +13,13 @@
 # that way.
 #
 
-if [ "$1" = "--help" ]
-then
+function print_usage() {
 	echo "\nUtility to setup a bsd-based system for Wireshark Development.\n"
 	echo "The basic usage installs the needed software\n\n"
 	echo "Usage: $0 [--install-optional] [...other options...]\n"
 	echo "\t--install-optional: install optional software as well"
 	echo "\t[other]: other options are passed as-is to pkg manager.\n"
-	exit 1
-fi
-
-# Check if the user is root
-if [ $(id -u) -ne 0 ]
-then
-	echo "You must be root."
-	exit 1
-fi
+}
 
 OPTIONS=
 for op
@@ -36,11 +27,22 @@ do
 	if [ "$op" = "--install-optional" ]
 	then
 		ADDITIONAL=1
+	elif [ "$op" = "--help" ]
+	then
+		print_usage
+		exit 0
 	else
 		OPTIONS="$OPTIONS $op"
 	fi
 done
 
+# Check if the user is root
+if [ $(id -u) -ne 0 ]
+then
+	echo "You must be root."
+	exit 1
+fi
+
 BASIC_LIST="\
 	cmake \
 	qt5 \

tools/debian-setup.sh

@@ -13,8 +13,7 @@
 
 set -e -u -o pipefail
 
-if [ "$1" = "--help" ]
-then
+function print_usage() {
 	printf "\\nUtility to setup a debian-based system for Wireshark Development.\\n"
 	printf "The basic usage installs the needed software\\n\\n"
 	printf "Usage: %s [--install-optional] [--install-deb-deps] [...other options...]\\n" "$0"
@@ -22,15 +21,7 @@ then
 	printf "\\t--install-deb-deps: install packages required to build the .deb file\\n"
 	printf "\\t--install-test-deps: install packages required to run all tests\\n"
 	printf "\\t[other]: other options are passed as-is to apt\\n"
-	exit 1
-fi
-
-# Check if the user is root
-if [ "$(id -u)" -ne 0 ]
-then
-	echo "You must be root."
-	exit 1
-fi
+}
 
 ADDITIONAL=0
 DEBDEPS=0
@@ -38,6 +29,10 @@ TESTDEPS=0
 OPTIONS=
 for arg; do
 	case $arg in
+		--help)
+			print_usage
+			exit 0
+			;;
 		--install-optional)
 			ADDITIONAL=1
 			;;
@@ -53,6 +48,13 @@ for arg; do
 	esac
 done
 
+# Check if the user is root
+if [ "$(id -u)" -ne 0 ]
+then
+	echo "You must be root."
+	exit 1
+fi
+
 BASIC_LIST="gcc \
 	g++\
 	libglib2.0-dev \

tools/msys2-setup.sh

@@ -11,8 +11,7 @@
 # that way.
 #
 
-if [ "$1" = "--help" ]
-then
+function print_usage() {
 	printf "\\nUtility to setup an MSYS2 MinGW-w64 system for Wireshark development.\\n"
 	printf "The basic usage installs the needed software\\n\\n"
 	printf "Usage: %s [--install-optional] [...other options...]\\n" "$0"
@@ -21,8 +20,7 @@ then
 	printf "\\t--install-all: install everything\\n"
 	printf "\\t[other]: other options are passed as-is to pacman\\n"
 	printf "\\tPass --noconfirm to bypass any \"are you sure?\" messages.\\n"
-	exit 1
-fi
+}
 
 ADDITIONAL=0
 TESTDEPS=0
@@ -30,6 +28,10 @@ LUA=0
 OPTIONS=
 for arg; do
 	case $arg in
+		--help)
+			print_usage
+			exit 0
+			;;
 		--install-optional)
 			ADDITIONAL=1
 			;;

tools/rpm-setup.sh

@@ -13,29 +13,24 @@
 
 set -e -u -o pipefail
 
-if [ "$1" = "--help" ]
-then
+function print_usage() {
 	echo "\nUtility to setup a rpm-based system for Wireshark Development.\n"
 	echo "The basic usage installs the needed software\n\n"
 	echo "Usage: $0 [--install-optional] [...other options...]\n"
 	echo "\t--install-optional: install optional software as well"
 	echo "\t--install-rpm-deps: install packages required to build the .rpm file\\n"
 	echo "\t[other]: other options are passed as-is to the packet manager\n"
-	exit 1
-fi
-
-# Check if the user is root
-if [ $(id -u) -ne 0 ]
-then
-	echo "You must be root."
-	exit 1
-fi
+}
 
 ADDITIONAL=0
 RPMDEPS=0
 OPTIONS=
 for arg; do
 	case $arg in
+		--help)
+			print_usage
+			exit 0
+			;;
 		--install-optional)
 			ADDITIONAL=1
 			;;
@@ -48,6 +43,13 @@ for arg; do
 	esac
 done
 
+# Check if the user is root
+if [ $(id -u) -ne 0 ]
+then
+	echo "You must be root."
+	exit 1
+fi
+
 BASIC_LIST="cmake \
 	gcc \
 	gcc-c++ \