disable test_ratchet on dynamically-linked Windows builds

tests/CMakeLists.txt

 enable_testing()
 
-foreach(test IN ITEMS
+set(TEST_LIST
     test_base64
     test_crypto
     test_group_session
@@ -12,11 +12,20 @@ foreach(test IN ITEMS
     test_olm_sha256
     test_olm_signature
     test_olm_using_malloc
-    test_ratchet
     test_session
     test_pk
     test_sas
-    )
+  )
+
+if(NOT (${CMAKE_SYSTEM_NAME} MATCHES "Windows" AND BUILD_SHARED_LIBS))
+  # test_ratchet doesn't work on Windows when building a DLL, because it tries
+  # to use internal symbols, so only enable it if we're not on Windows, or if
+  # we're building statically
+  set(TEST_LIST ${TEST_LIST} test_ratchet)
+  add_test(Ratchet test_ratchet)
+endif()
+
+foreach(test IN ITEMS ${TEST_LIST})
 add_executable(${test} ${test}.cpp)
 target_include_directories(${test} PRIVATE include)
 target_link_libraries(${test} Olm::Olm)
@@ -33,7 +42,6 @@ add_test(OlmDecrypt test_olm_decrypt)
 add_test(OlmSha256 test_olm_sha256)
 add_test(OlmSignature test_olm_signature)
 add_test(OlmUsingMalloc test_olm_using_malloc)
-add_test(Ratchet test_ratchet)
 add_test(Session test_session)
 add_test(PublicKey test_session)
 add_test(SAS test_sas)