Add an --enable-backtraces option to configure to determine
whether or not we want to print out backtrace information. Useful
for libraries that don't need backtrace information on a crash.

rdar://11844710

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@164426 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Support/Unix/Signals.inc b/lib/Support/Unix/Signals.inc
index b7f83b6..7d161a6 100644
--- a/lib/Support/Unix/Signals.inc
+++ b/lib/Support/Unix/Signals.inc
@@ -243,7 +243,7 @@
 // On glibc systems we have the 'backtrace' function, which works nicely, but
 // doesn't demangle symbols.
 static void PrintStackTrace(void *) {
-#ifdef HAVE_BACKTRACE
+#if defined(HAVE_BACKTRACE) && defined(ENABLE_BACKTRACE)
   static void* StackTrace[256];
   // Use backtrace() to output a backtrace on Linux systems with glibc.
   int depth = backtrace(StackTrace,