Bug#851371: libllvm3.9-dbg: lots of "Could not find DWO" and "in read in psymtab, but not in symtab" warnings

[Nicolás Alvarez]

This doesn't prevent breakpoints, but it seems to prevent inspecting
local variables. Running "bt full" in gdb says "no locals" for every
stack frame in LLVM or Clang libraries.

By the way, this bug seems to be related:
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1413646

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Nicolás