Support building src/tools/linux/dump_syms/dump_syms on OS X

This allows dumping ELF binaries on OS X, which is useful for folks who build
Android NDK code under OS X.

[jaysoffian]

I've tested this by running the ported dump_syms against a few SO's on Linux and
OS X and confirmed identical output.

About my approach to allow this to compile on OS X:

- I copied the necessary Linux headers into src/third_party/linux

- I redefined some of the sys_* methods to use their non sys_ counterpart in
memory_mapped_file. Something similar is already done in memory.h

- OS X doesn't have a memrchr.c. I just used one of the common implementation
that can be found floating around the web, and retained its copyright, and added
my own header. Perhaps adding a new pair of source files is overkill. I could
alternately write my own implementation and add it to linux_libc_support.{h,cc}
as my_memrchr, then add a define from "memrchr" to my_memrchr. But that's not
really the intention of the my_ functions in linux_libc_support, so I didn't do
that. Alternately, I originally had just static inlined memrchr at the top of
elf_symbols_to_module.cc, behind an __APPLE__ #ifdef.

[jaysoffian]

BTW, I have an individual CLA with Google, but this contribution is in my
capacity as a Yahoo employee. Yahoo has signed Google's CLA as a company.

[jaysoffian]

Okay, done futzing with it now till I receive feedback. :-)

[Ted Mielczarek]

https://breakpad.appspot.com/8684002/diff/180001/src/third_party/linux/includ...
File src/third_party/linux/include/bits/link.h (right):

https://breakpad.appspot.com/8684002/diff/180001/src/third_party/linux/includ...
src/third_party/linux/include/bits/link.h:7: version 2.1 of the License, or (at
your option) any later version.
This is going to be a deal-breaker. We can't import LGPL source into the
Breakpad tree, it's BSD licensed.

[jaysoffian]

https://breakpad.appspot.com/8684002/diff/180001/src/third_party/linux/includ...
File src/third_party/linux/include/bits/link.h (right):

https://breakpad.appspot.com/8684002/diff/180001/src/third_party/linux/includ...
src/third_party/linux/include/bits/link.h:7: version 2.1 of the License, or (at
your option) any later version.
On 2015/03/03 13:15:02, Ted Mielczarek wrote:
> This is going to be a deal-breaker. We can't import LGPL source into the
> Breakpad tree, it's BSD licensed.

Eeek. I'll look into using http://sourceforge.net/p/elftoolchain/wiki/Home/
instead. Other suggestions appreciated.