Index: llvm/unittests/Passes/CMakeLists.txt
===================================================================
--- llvm/unittests/Passes/CMakeLists.txt
+++ llvm/unittests/Passes/CMakeLists.txt
@@ -7,6 +7,15 @@
   add_definitions(-DLLVM_ENABLE_PLUGINS)
 endif()
 
+# The plugin expects to not link against the Support and Core libraries
+# (otherwise there are multiple definitions of the same command line option
+# in the binary), but expects them to exist in the process loading the plugin.
+# This doesn't work with DLLs on Windows (where a shared library can't have
+# undefined references), so just skip this testcase in such configurations.
+if (WIN32 AND BUILD_SHARED_LIBS)
+  return()
+endif()
+
 set(LLVM_LINK_COMPONENTS Support Passes Core)
 add_llvm_unittest(PluginsTests
   PluginsTest.cpp