Always skip recovery SysV shared memory tests on Windows

The test for SysV support currently involves looking for the perl
modules IPC::SharedMem and IPC::SysV. However, the perl on msys2 has
these modules but the tests fail. Therefore, force skipping the tests on
Windows platforms unconditionally.

Discussion: https://postgr.es/m/176e86ba-1a46-9d8c-5ae4-9865a463b411@2ndQuadrant.com

src/test/recovery/t/017_shm.pl

@@ -18,7 +18,7 @@ eval {
 	require IPC::SysV;
 	IPC::SysV->import(qw(IPC_CREAT IPC_EXCL S_IRUSR S_IWUSR));
 };
-if ($@)
+if ($@ || $windows_os)
 {
 	plan skip_all => 'SysV shared memory not supported by this platform';
 }