Do not adjust PT_GNU_STACK segment

Bug: http://b/20687795
Bug: http://b/18051137
Change-Id: Ie8af3892cfbebcc0249e7981284c4ad97ff40317
diff --git a/tools/relocation_packer/src/elf_file.cc b/tools/relocation_packer/src/elf_file.cc
index d06bd63..102d614 100644
--- a/tools/relocation_packer/src/elf_file.cc
+++ b/tools/relocation_packer/src/elf_file.cc
@@ -312,6 +312,13 @@
   for (size_t i = 0; i < count; ++i) {
     typename ELF::Phdr* program_header = &program_headers[i];
 
+    // Do not adjust PT_GNU_STACK - it confuses gdb and results
+    // in incorrect unwinding if the executable is stripped after
+    // packing.
+    if (program_header->p_type == PT_GNU_STACK) {
+      continue;
+    }
+
     if (program_header->p_offset > hole_start) {
       // The hole start is past this segment, so adjust offset.
       program_header->p_offset += hole_size;