swift234

[Driver] Set [DY]LD_LIBRARY_PATH when building an interpreter job.

That's DYLD_LIBRARY_PATH on OS X and LD_LIBRARY_PATH on Linux for -L,
and DYLD_FRAMEWORK_PATH on OS X for -F.

Note that this commit doesn't actually include the setenv calls yet, so an
end-to-end test is coming in the next commit.

Part of rdar://problem/23588774