[libFuzzer] make sure the input data is not overwritten in the fuzz target (if it is -- report an error)

llvm-svn: 302494
diff --git a/llvm/lib/Fuzzer/test/overwrite-input.test b/llvm/lib/Fuzzer/test/overwrite-input.test
new file mode 100644
index 0000000..81c2790
--- /dev/null
+++ b/llvm/lib/Fuzzer/test/overwrite-input.test
@@ -0,0 +1,2 @@
+RUN: not LLVMFuzzer-OverwriteInputTest 2>&1 | FileCheck %s
+CHECK: ERROR: libFuzzer: fuzz target overwrites it's const input