Bug#848368: llvm-toolchain-3.9: Please add ELF symbols versions to the libraries

[Rebecca N. Palmer]

Rebuilding beignet and mesa against this llvm succeeds, and this beignet 
works.  (beignet is statically linked to LLVM/Clang, so we can't use it 
as a test of whether non-rebuilt rdeps work.)

blender+pocl-opencl-icd still crashes, with the bad jump being from 3.8 
to a versioned 3.9 symbol, but I suspect that just means LLVM 3.8 also 
needs a similar fix (possibly even the same one - I didn't try mostly 
because that means another hours-long build).

blender without pocl-opencl-icd works, with either rebuilt or 
non-rebuilt mesa, but given that this is in a chroot drawing to a Xephyr 
window, it may not be a good test of mesa.

$ cat /tmp/blender.crash.txt
# Blender 2.78 (sub 0), Unknown revision

# backtrace
blender(BLI_system_backtrace+0x30) [0x7f3dc227fec0]
blender(+0x1023101) [0x7f3dc1828101]
/lib/x86_64-linux-gnu/libc.so.6(+0x33040) [0x7f3db6597040]
/usr/lib/x86_64-linux-gnu/libLLVM-3.9.so.1(_ZN4llvm2cl6Option9setArgStrENS_9StringRefE+0x9d) 
[0x7f3d8f2d2eed]
/usr/lib/x86_64-linux-gnu/libLLVM-3.8.so.1(+0x54f10b) [0x7f3d83a9b10b]
/usr/lib/x86_64-linux-gnu/libLLVM-3.8.so.1(+0x54f348) [0x7f3d83a9b348]
/lib64/ld-linux-x86-64.so.2(+0xf64a) [0x7f3dc05ee64a]
[...]
$ objdump -T /usr/lib/x86_64-linux-gnu/libLLVM-3.9.so.1 | grep 
_ZN4llvm2cl6Option9setArgStrENS_9StringRefE
000000000069ae50 g    DF .text	000000000000034d  LLVM_3.9 
_ZN4llvm2cl6Option9setArgStrENS_9StringRefE