binutils: patch to fix https://sourceware.org/bugzilla/show_bug.cgi?id=16177

This bug was preventing one compiling Haskell programs from `pkgsMusl` for
armv7.

`nix-build --argstr crossSystem "armv7l-linux" -A pkgsMusl.haskellPackages.hello`
succeeds with this patch.

The patch is Nick Clifton's one, rebased by @ericson2314 here
https://sourceware.org/bugzilla/show_bug.cgi?id=16177#c6

Although there was some talk about the efficacy of the binutils patch
(https://sourceware.org/bugzilla/show_bug.cgi?id=16177#c9) the resulting
binary seems to run without issue on the target platform. Jessica's
patch there caused ld to fail linking some programs. Nick's proposed
patch has worked well in my testing so far (a Haskell project of some
small complexity cross compiled with musl to armv7).

pkgs/development/tools/misc/binutils/R_ARM_COPY.patch

@@ -0,0 +1,29 @@
+@@ -, +, @@ 
+---
+ bfd/elf32-arm.c | 8 +++++++-
+ 1 file changed, 7 insertions(+), 1 deletion(-)
+--- a/bfd/elf32-arm.c	
++++ a/bfd/elf32-arm.c	
+@@ -15398,7 +15398,11 @@ elf32_arm_adjust_dynamic_symbol (struct bfd_link_info * info,
+      linker to copy the initial value out of the dynamic object and into
+      the runtime process image.  We need to remember the offset into the
+      .rel(a).bss section we are going to use.  */
+-  if ((h->root.u.def.section->flags & SEC_READONLY) != 0)
++  if (info->nocopyreloc == 0
++      && (h->root.u.def.section->flags & SEC_ALLOC) != 0
++      /* PR 16177: A copy is only needed if the input section is readonly.  */
++      && (h->root.u.def.section->flags & SEC_READONLY) != 0
++      && h->size != 0)
+     {
+       s = globals->root.sdynrelro;
+       srel = globals->root.sreldynrelro;
+@@ -15410,6 +15414,8 @@ elf32_arm_adjust_dynamic_symbol (struct bfd_link_info * info,
+     }
+   if (info->nocopyreloc == 0
+       && (h->root.u.def.section->flags & SEC_ALLOC) != 0
++      /* PR 16177: A copy is only needed if the input section is readonly.  */
++      && (h->root.u.def.section->flags & SEC_READONLY) != 0
+       && h->size != 0)
+     {
+       elf32_arm_allocate_dynrelocs (info, srel, 1);
+

pkgs/development/tools/misc/binutils/default.nix

@@ -101,6 +101,14 @@ stdenv.mkDerivation {
     ./patches/2.31/0001-x86-Properly-add-X86_ISA_1_NEEDED-property.patch
   ]
   ++ lib.optional stdenv.targetPlatform.isiOS ./support-ios.patch
+  ++ # This patch was suggested by Nick Clifton to fix
+     # https://sourceware.org/bugzilla/show_bug.cgi?id=16177
+     # It can be removed when that 7-year-old bug is closed.
+     # This binutils bug causes GHC to emit broken binaries on armv7, and
+     # indeed GHC will refuse to compile with a binutils suffering from it. See
+     # this comment for more information:
+     # https://gitlab.haskell.org/ghc/ghc/issues/4210#note_78333
+     lib.optional stdenv.targetPlatform.isAarch32 ./R_ARM_COPY.patch
   ;
 
   outputs = [ "out" "info" "man" ];