lld: Omit PT_NOTE for SHT_NOTE without SHF_ALLOC

lld: Omit PT_NOTE for SHT_NOTE without SHF_ALLOC

A non-alloc note section should not have a PT_NOTE program header.

Found while linking ghc (Haskell compiler) with lld on FreeBSD.  Haskell
emits a .debug-ghc-link-info note section (as the name suggests, it
contains link info) as a SHT_NOTE section without SHF_ALLOC set.

For this case ld.bfd does not emit a PT_NOTE segment for
.debug-ghc-link-info.  lld previously emitted a PT_NOTE with p_vaddr = 0
and FreeBSD's rtld segfaulted when trying to parse a note at address 0.

LLVM PR:	https://llvm.org/pr37361
LLVM review:	https://reviews.llvm.org/D46623

PR:		226872
Reviewed by:	dim
Sponsored by:	The FreeBSD Foundation