Improve VPN setup

- Install package libcrypt-dev on Ubuntu/Debian, and package
  libxcrypt-devel on CentOS 8+, which are needed for Libreswan
  compilation. This change fixes VPN setup on Ubuntu 26.04.

extras/vpnupgrade_centos.sh

@@ -171,6 +171,12 @@ install_pkgs_1() {
       libcap-ng-devel libselinux-devel curl-devel nss-tools \
       flex bison gcc make wget sed tar >/dev/null
   ) || exiterr2
+  if [ "$os_ver" != 7 ]; then
+    (
+      set -x
+      yum -y -q install libxcrypt-devel >/dev/null
+    ) || exiterr2
+  fi
 }
 
 install_pkgs_2() {

extras/vpnupgrade_ubuntu.sh

@@ -177,7 +177,7 @@ install_pkgs() {
     set -x
     apt-get -yqq install libnss3-dev libnspr4-dev pkg-config \
       libpam0g-dev libcap-ng-dev libcap-ng-utils libselinux1-dev \
-      $p1 libnss3-tools libevent-dev libsystemd-dev \
+      $p1 libnss3-tools libevent-dev libsystemd-dev libcrypt-dev \
       flex bison gcc make wget sed >/dev/null
   ) || exiterr2
   if { [ "$os_type" = "ubuntu" ] && [ -n "$ubuntu_ver" ] \

vpnsetup_centos.sh

@@ -277,6 +277,12 @@ install_vpn_pkgs_1() {
       libcap-ng-devel libselinux-devel curl-devel nss-tools \
       flex bison gcc make util-linux ppp >/dev/null
   ) || exiterr2
+  if [ "$os_ver" != 7 ]; then
+    (
+      set -x
+      yum -y -q install libxcrypt-devel >/dev/null
+    ) || exiterr2
+  fi
 }
 
 install_vpn_pkgs_2() {

vpnsetup_ubuntu.sh

@@ -282,7 +282,7 @@ install_vpn_pkgs() {
     set -x
     apt-get -yqq install libnss3-dev libnspr4-dev pkg-config \
       libpam0g-dev libcap-ng-dev libcap-ng-utils libselinux1-dev \
-      $p1 flex bison gcc make libnss3-tools \
+      $p1 flex bison gcc make libnss3-tools libcrypt-dev \
       libevent-dev libsystemd-dev uuid-runtime ppp xl2tpd >/dev/null
   ) || exiterr2
   if { [ "$os_type" = "ubuntu" ] && [ -n "$ubuntu_ver" ] \