[libFuzzer] Portably disassemble and find calls to sanitizer_cov_trace_pc_guard.

Instead of directly using objdump, which is not present on Windows, we consider
different tools depending on the platform.
For Windows, we consider dumpbin and llvm-objdump.

Differential Revision: https://reviews.llvm.org/D28635

llvm-svn: 292739
diff --git a/llvm/lib/Fuzzer/FuzzerUtilPosix.cpp b/llvm/lib/Fuzzer/FuzzerUtilPosix.cpp
index e8d48dc..0161309 100644
--- a/llvm/lib/Fuzzer/FuzzerUtilPosix.cpp
+++ b/llvm/lib/Fuzzer/FuzzerUtilPosix.cpp
@@ -118,6 +118,14 @@
   return memmem(Data, DataLen, Patt, PattLen);
 }
 
+std::string DisassembleCmd(const std::string &FileName) {
+  return "objdump -d " + FileName;
+}
+
+std::string SearchRegexCmd(const std::string &Regex) {
+  return "grep '" + Regex + "'";
+}
+
 }  // namespace fuzzer
 
 #endif // LIBFUZZER_POSIX