Merge pull request #29821 from drodriguez/windows-fix-host-variant-case

[windows] Compare SWIFT_HOST_VARIANT against lowercase value.

Author: drodriguez

unittests/runtime/CMakeLists.txt

@@ -85,7 +85,7 @@ if(("${SWIFT_HOST_VARIANT_SDK}" STREQUAL "${SWIFT_PRIMARY_VARIANT_SDK}") AND
                              PRIVATE
                                swiftCore_EXPORTS)
 
-  if(SWIFT_HOST_VARIANT STREQUAL WINDOWS)
+  if(SWIFT_HOST_VARIANT STREQUAL "windows")
     target_compile_definitions(SwiftRuntimeTests PRIVATE
       _ENABLE_EXTENDED_ALIGNED_STORAGE)
   endif()