sshserver.pl: use cached Win32 environment check variable
diff --git a/tests/sshserver.pl b/tests/sshserver.pl
index 59ea0ae..084b4a8 100644
--- a/tests/sshserver.pl
+++ b/tests/sshserver.pl
@@ -405,7 +405,7 @@
 my $pidfile_config = $pidfile;
 my $sftpsrv_config = $sftpsrv;
 
-if ($^O eq 'MSWin32' || $^O eq 'cygwin' || $^O eq 'msys') {
+if (pathhelp::os_is_win()) {
     # Ensure to use MinGW/Cygwin paths
     $clipubkeyf_config = pathhelp::build_sys_abs_path($clipubkeyf_config);
     $hstprvkeyf_config = pathhelp::build_sys_abs_path($hstprvkeyf_config);
@@ -797,7 +797,7 @@
 my $identity_config = abs_path("$path/$identity");
 my $knownhosts_config = abs_path("$path/$knownhosts");
 
-if ($^O eq 'MSWin32' || $^O eq 'cygwin' || $^O eq 'msys') {
+if (pathhelp::os_is_win()) {
     # Ensure to use MinGW/Cygwin paths
     $identity_config = pathhelp::build_sys_abs_path($identity_config);
     $knownhosts_config = pathhelp::build_sys_abs_path($knownhosts_config);