[PATCH] [lld] [ELF] Support for general dynamic TLS relocations on X86_64

[Shankar Kalpathi Easwaran]

canBeNullAtBuildTime is associated with a weak symbol while __tls_get_addr is not a weak symbo in the writer, which changes the symbol semantics.

The reason I was mentioning about removing the __tls_get_addr atom for the executable is for the code was not PIC.

http://reviews.llvm.org/D5505