test/recipes/80-test_pkcs12.t: handle lack of Win32::API.

So far check for availability of Win32::API served as implicit check
for $^O being MSWin32. Reportedly it's not safe assumption, and check
for MSWin32 has to be explicit.

Reviewed-by: Matt Caswell <matt@openssl.org>
Reviewed-by: Rich Salz <rsalz@openssl.org>
(Merged from #5416)

(cherry picked from commit d4c499f)

test/recipes/80-test_pkcs12.t

@@ -41,6 +41,8 @@ if (eval { require Win32::API; 1; }) {
         SetConsoleOutputCP(1253);
         $pass = Encode::encode("cp1253",Encode::decode("utf-8",$pass));
     }
+} elsif ($^O eq "MSWin32") {
+    plan skip_all => "Win32::API unavailable";
 } else {
     # Running MinGW tests transparently under Wine apparently requires
     # UTF-8 locale...