tests: Remove Cygwin WinMain workaround

src/test/fuzz/fuzz.cpp

@@ -40,14 +40,9 @@ extern "C" int LLVMFuzzerInitialize(int* argc, char*** argv)
     return 0;
 }
 
-// Disabled under WIN32 due to clash with Cygwin's WinMain.
-#ifndef WIN32
 // Declare main(...) "weak" to allow for libFuzzer linking. libFuzzer provides
 // the main(...) function.
-__attribute__((weak))
-#endif
-int
-main(int argc, char** argv)
+__attribute__((weak)) int main(int argc, char** argv)
 {
     initialize();
 #ifdef __AFL_INIT