Set sonames for shared NaClSdk libraries
Set sonames for shared NaClSdk libraries

This change is probably somewhat hacky as it sets the appropriate link flags in a very explicit way. However, the case when we need something more general here is unlikely.

Anyway, sonames are needed to proceed with building shared libraries on win, and having this change in early is important. I'll revise the change for generality when shared libraries are built on all host platforms. 

BUG=http://code.google.com/p/nativeclient/issues/detail?id=1597
TEST=check the presence of SONAME entry with objdump -p
Review URL: http://codereview.chromium.org/7014018

git-svn-id: 721b910a23eff8a86f00c8fd261a7587cddf18f8@5270 fcba33aa-ac0c-11dd-b9e7-8d5594d729c2

nacl-webkit/native_client,nacl-webkit/native_client,sbc100/native_client,nacl-webkit/native_client,sbc100/native_client,nacl-webkit/native_client,sbc100/native_client,sbc100/native_client,sbc100/native_client,sbc100/native_client,nacl-webkit/native_client