The `shobj-conf` script imported from bash seems to not support the
latest OS X. This makes sure that `SHOBJ_LDFLAG=-dynamiclib` is output
for Darwin10+ (latest version is Darwin 13.0).
Given the `-o <HOST-OS>` parameter, the script generates environment
variables with information how to compile dynamically loadable libraries
for that system.
Imported from bash-3.2.48