[GHC] #13541: Make it easier to use the gold linker

[GHC]

#13541: Make it easier to use the gold linker
-------------------------------------+-------------------------------------
        Reporter:  bgamari           |                Owner:  (none)
            Type:  feature request   |               Status:  patch
        Priority:  highest           |            Milestone:  8.2.1
       Component:  Compiler          |              Version:  8.0.1
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:  #13810, #13739    |  Differential Rev(s):  Phab:D3449,
       Wiki Page:                    |  Phab:D3694
-------------------------------------+-------------------------------------

Comment (by Ben Gamari <ben@…>):

 In [changeset:"960918bd1f7e3811845a525ba85bbd390ddf28c8/ghc"
 960918bd/ghc]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="960918bd1f7e3811845a525ba85bbd390ddf28c8"
 Add -fuse-ld flag to CFLAGS during configure

 The decisions made by configure later in the script may depend upon the
 linker used. Consequently, it is important that configure uses the same
 linker as GHC will eventually use.

 For instance, on Nix I found that a program requiring `libpthread` would
 link fine with only `-lrt` when linked with BFD ld. However, with gold
 we needed to explicitly provide the `-lpthread` dependency. Presumably
 the former would happily loaded any `NEEDED` libraries whereas the
 latter wants them explicitly given. Regardless, since `configure`'s
 `NEED_PTHREAD_LIB` check didn't use the `-fuse-ld` flag that GHC would
 eventually use, we inferred the wrong value, resulting in link errors
 later in the build.

 Test Plan: Validate

 Reviewers: austin, hvr

 Subscribers: rwbarton, thomie, erikd

 GHC Trac Issues: #13541

 Differential Revision: https://phabricator.haskell.org/D3694
 }}}

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13541#comment:31>
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