[ELF] Fix alignment for dynamic relocation sections.

The sections .rela/.rel.(*) have a alignment of 2 in the final image created by
the linker. This needs to be properly set to the right alignment depending on
the architecture(32/64bits).

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@201740 91177308-0d34-0410-b5e6-96231b3b80d8
[ELF] Dont generate PHDR when creating dynamic libraries.

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@201741 91177308-0d34-0410-b5e6-96231b3b80d8