kernel32/tests: use ret in load_blackbox() (try 2)

[Austin English]

Changes from try 1:
Set LastError first, and print GetLastError as a decimal.

-- 
-Austin
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diff --git a/dlls/kernel32/tests/debugger.c b/dlls/kernel32/tests/debugger.c
index e116c9d..fa96767 100644
--- a/dlls/kernel32/tests/debugger.c
+++ b/dlls/kernel32/tests/debugger.c
@@ -143,7 +143,9 @@ static int load_blackbox(const char* logfile, void* blackbox, int size)
         ok(0, "unable to open '%s'\n", logfile);
         return 0;
     }
+    SetLastError(0xdeadbeef);
     ret=ReadFile(hFile, blackbox, size, &read, NULL);
+    ok(ret, "ReadFile failed: %d\n", GetLastError());
     ok(read == size, "wrong size for '%s': read=%d\n", logfile, read);
     CloseHandle(hFile);
     return 1;