Search for llvm-symbolizer binary in the same directory as argv[0], before
looking for it along $PATH. This allows installs of LLVM tools outside of
$PATH to find the symbolizer and produce pretty backtraces if they crash.

llvm-svn: 272232
diff --git a/llvm/tools/llvm-mcmarkup/llvm-mcmarkup.cpp b/llvm/tools/llvm-mcmarkup/llvm-mcmarkup.cpp
index 5654313..0be3c71 100644
--- a/llvm/tools/llvm-mcmarkup/llvm-mcmarkup.cpp
+++ b/llvm/tools/llvm-mcmarkup/llvm-mcmarkup.cpp
@@ -208,7 +208,7 @@
 
 int main(int argc, char **argv) {
   // Print a stack trace if we signal out.
-  sys::PrintStackTraceOnErrorSignal();
+  sys::PrintStackTraceOnErrorSignal(argv[0]);
   PrettyStackTraceProgram X(argc, argv);
 
   llvm_shutdown_obj Y;  // Call llvm_shutdown() on exit.