Skip ROCM/test/opt_pass_plugin on Windows while broken. (iree-org#18823)

This test is failing to link on CI machines and failing to run on my
local machine. See discussion starting here:
iree-org#18347 (comment).

Disabling for now so we can (hopefully) get a working nightly Windows
build and release for the first time in several weeks, but we could also
revert the PR or fix-forward.

compiler/plugins/target/ROCM/test/opt_pass_plugin/CMakeLists.txt

@@ -1,3 +1,8 @@
+# Disabled on Windows until the shared library handling is cross-platform.
+if(CMAKE_SYSTEM_NAME MATCHES "Windows")
+  return()
+endif()
+
 iree_cc_library(
   NAME
     GPUHello