MSVC: do not build fuzz/ and style/ tests on Windows

Stuff like `waitpid` is a sure sign that `fuzz/` is better skipped when
building on Windows. The `style/` is about compiling like C++ and about
making sure that all files which need some functions include `compat.h`.
I don't feel like researching how to do `-Werror=c++-compat` on MSVC,
and if the `compat.h` is ever missing, the MSVC build will yell loudly.
diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
index b68d934..8f3a34d 100644
--- a/tests/CMakeLists.txt
+++ b/tests/CMakeLists.txt
@@ -36,10 +36,12 @@
 endfunction()
 
 if(ENABLE_TESTS)
-    add_subdirectory(style)
     add_subdirectory(plugins)
     add_subdirectory(utests)
-    add_subdirectory(fuzz)
+    if(NOT WIN32)
+        add_subdirectory(style)
+        add_subdirectory(fuzz)
+    endif()
 endif()
 if(ENABLE_PERF_TESTS)
     add_subdirectory(perf)