sys-devel/binutils: apply linker search path fixes from Chewi for prefix

Quoting Chewi on the PR for posterity:
"""
The first of these changes fixes two related issues with prefixed and crossdev environments.
The prefix issue is detailed in Gentoo bug #892549. The crossdev issue can be reproduced by trying something like:

USE="-python icu" aarch64-unknown-linux-gnu-emerge libxml2

The second of these changes is not essential, but it does make bfd's behaviour
in this area more consistent with the other linkers, which have not experienced these issues at all.

I'm not sure what upstream will make of these changes, particularly the second one,
but it is interesting that even gold does not behave the same way as bfd here.

Perhaps we can give them some exposure in Gentoo for a while before seeing what they think.
The second change would not be submitted upstream as-is because fully removing the ld.so.conf feature is a much bigger diff.
"""

This patch is, for now, only applied for prefix. It should be safe
on other systems but the issue is more pressing on prefix given a recent
migration.

Bug: https://bugs.gentoo.org/892549
Thanks-to: James Le Cuirot <chewi@gentoo.org>
Signed-off-by: Sam James <sam@gentoo.org>

1 files changed, 74 insertions, 0 deletions

diff --git a/sys-devel/binutils/files/binutils-2.40-linker-search-path.patch b/sys-devel/binutils/files/binutils-2.40-linker-search-path.patch
new file mode 100644
index 000000000000..7423f8d70556
--- /dev/null
+++ b/sys-devel/binutils/files/binutils-2.40-linker-search-path.patch
@@ -0,0 +1,74 @@
+https://bugs.gentoo.org/892549
+https://github.com/gentoo/binutils-gdb/pull/4
+
+From 1601840f9f2397edd56177871527a198a14277bd Mon Sep 17 00:00:00 2001
+From: James Le Cuirot <chewi@gentoo.org>
+Date: Sat, 11 Feb 2023 15:15:20 +0000
+Subject: [PATCH 1/2] ldelf.c: Always consider -L arguments when handling
+ DT_NEEDED
+
+This is for consistency with other linkers, including gold. Without
+this, we typically rely on ld.so.conf to find libraries such as
+libstdc++.so.6, while other linkers do not use this file at all.
+--- a/ld/ldelf.c
++++ b/ld/ldelf.c
+@@ -1090,8 +1090,8 @@ ldelf_handle_dt_needed (struct elf_link_hash_table *htab,
+ 	 linker will search.  That means that we want to use
+ 	 rpath_link, rpath, then the environment variable
+ 	 LD_LIBRARY_PATH (native only), then the DT_RPATH/DT_RUNPATH
+-	 entries (native only), then the linker script LIB_SEARCH_DIRS.
+-	 We do not search using the -L arguments.
++	 entries (native only), then the linker script LIB_SEARCH_DIRS,
++	 then the -L arguments.
+ 
+ 	 We search twice.  The first time, we skip objects which may
+ 	 introduce version mismatches.  The second time, we force
+@@ -1165,11 +1165,7 @@ ldelf_handle_dt_needed (struct elf_link_hash_table *htab,
+ 	  len = strlen (l->name);
+ 	  for (search = search_head; search != NULL; search = search->next)
+ 	    {
+-	      char *filename;
+-
+-	      if (search->cmdline)
+-		continue;
+-	      filename = (char *) xmalloc (strlen (search->name) + len + 2);
++	      char *filename = (char *) xmalloc (strlen (search->name) + len + 2);
+ 	      sprintf (filename, "%s/%s", search->name, l->name);
+ 	      nn.name = filename;
+ 	      if (ldelf_try_needed (&nn, force, is_linux))
+
+From 8afc65c8d8c0fff2f686ddd8eb9023c7ebabcca9 Mon Sep 17 00:00:00 2001
+From: James Le Cuirot <chewi@gentoo.org>
+Date: Sat, 11 Feb 2023 15:18:58 +0000
+Subject: [PATCH 2/2] ldelf.c: Do not search for libraries using ld.so.conf
+
+Other linkers do not do this. It is problematic for Gentoo Linux,
+because crossdev installs libraries such as libstdc++.so.6 outside of
+the sysroot.
+--- a/ld/ld.texi
++++ b/ld/ld.texi
+@@ -2355,7 +2355,9 @@ For a linker for a Linux system, if the file @file{/etc/ld.so.conf}
+ exists, the list of directories found in that file.  Note: the path
+ to this file is prefixed with the @code{sysroot} value, if that is
+ defined, and then any @code{prefix} string if the linker was
+-configured with the @command{--prefix=<path>} option.
++configured with the @command{--prefix=<path>} option. This has feature has
++been disabled on Gentoo Linux to make it consistent with the other
++linkers, which do not do this.
+ @item
+ For a native linker on a FreeBSD system, any directories specified by
+ the @code{_PATH_ELF_HINTS} macro defined in the @file{elf-hints.h}
+--- a/ld/ldelf.c
++++ b/ld/ldelf.c
+@@ -1156,10 +1156,6 @@ ldelf_handle_dt_needed (struct elf_link_hash_table *htab,
+ 	      if (is_freebsd
+ 		  && ldelf_check_ld_elf_hints (l, force, elfsize))
+ 		break;
+-
+-	      if (is_linux
+-		  && ldelf_check_ld_so_conf (l, force, elfsize, prefix))
+-		break;
+ 	    }
+ 
+ 	  len = strlen (l->name);
+