hwasan: Allow range of frame descriptors to be empty.

As of r349413 it's now possible for a binary to contain an empty
hwasan frame section. Handle that case simply by doing nothing.

Differential Revision: https://reviews.llvm.org/D55796

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@349428 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/hwasan/hwasan.cc b/lib/hwasan/hwasan.cc
index da95891..9f2328d 100644
--- a/lib/hwasan/hwasan.cc
+++ b/lib/hwasan/hwasan.cc
@@ -229,8 +229,8 @@
 void InitFrameDescriptors(uptr b, uptr e) {
   FrameDescription *beg = reinterpret_cast<FrameDescription *>(b);
   FrameDescription *end = reinterpret_cast<FrameDescription *>(e);
-  // Must have at least one entry, which we can use for a linked list.
-  CHECK_GE(end - beg, 1U);
+  if (beg == end)
+    return;
   AllFrames.push_back({beg, end});
   if (Verbosity())
     for (FrameDescription *frame_descr = beg; frame_descr < end; frame_descr++)