fix #25137, return value of dlclose on windows (#25175)

- Invert boolean value returned by Windows FreeLibrary so it matches
  that of POSIX dlclose
- Add test of jl_dlclose/Libdl.dlclose to test/libdl.jl

src/dlload.c

@@ -109,7 +109,7 @@ JL_DLLEXPORT int jl_dlclose(void *handle)
 {
 #ifdef _OS_WINDOWS_
     if (!handle) return -1;
-    return FreeLibrary((HMODULE) handle);
+    return !FreeLibrary((HMODULE) handle);
 #else
     dlerror(); /* Reset error status. */
     if (!handle) return -1;

test/libdl.jl

@@ -183,6 +183,20 @@ let dl = C_NULL
     end
 end
 
+# test dlclose
+# If dl is NULL, jl_dlclose should return -1 and dlclose should return false
+# dlclose should return true on success and false on failure
+let dl = C_NULL
+    @test -1 == ccall(:jl_dlclose, Cint, (Ptr{Void},), dl)
+    @test !Libdl.dlclose(dl)
+
+    dl = Libdl.dlopen_e("libccalltest")
+    @test dl != C_NULL
+
+    @test Libdl.dlclose(dl)
+    @test_skip !Libdl.dlclose(dl)   # Syscall doesn't fail on Win32
+end
+
 if Sys.KERNEL in (:Linux, :FreeBSD)
     ccall(:jl_read_sonames, Void, ())
 end