gnu: libunwind-julia: Fix build on i686-linux.

* gnu/packages/julia.scm (libunwind)[origin]<patches>: Add patch.
* gnu/packages/patches/libunwind-julia-fix-GCC10-fno-common.patch: New file.
* gnu/local/mk (dist_patch_DATA): Register it.

Signed-off-by: Efraim Flashner <efraim@flashner.co.il>

gnu/local.mk

@@ -1388,6 +1388,7 @@ dist_patch_DATA =						\
   %D%/packages/patches/libtirpc-hurd.patch			\
   %D%/packages/patches/libtommath-fix-linkage.patch		\
   %D%/packages/patches/libtool-skip-tests2.patch		\
+  %D%/packages/patches/libunwind-julia-fix-GCC10-fno-common.patch \
   %D%/packages/patches/libusb-0.1-disable-tests.patch		\
   %D%/packages/patches/libusb-for-axoloti.patch			\
   %D%/packages/patches/libutils-add-includes.patch		\

gnu/packages/julia.scm

@@ -71,13 +71,17 @@
         (base32
          "1y0l08k6ak1mqbfj6accf9s5686kljwgsl4vcqpxzk5n74wpm6a3"))
        (patches
-        (list
-         (julia-patch "libunwind-prefer-extbl"
-                      "0lr4dafw8qyfh8sw8hhbwkql1dlhqv8px7k81y2l20hhxfgnh2m1")
-         (julia-patch "libunwind-static-arm"
-                      "1jk3bmiw61ypcchqkk1fyg5wh8wpggk574wxyfyaic870zh3lhgq")
-         (julia-patch "libunwind-cfa-rsp"
-                      "1aswjhvysahhldbzh1afbf0hsjxrvs6xidsz2i7s1cjkjbdiia1z")))))
+        (append
+            ;; Fix linker issue for i686-linux because GCC10 changed default
+            ;; (see '-fno-common' option).
+            (search-patches "libunwind-julia-fix-GCC10-fno-common.patch")
+            (list
+             (julia-patch "libunwind-prefer-extbl"
+                          "0lr4dafw8qyfh8sw8hhbwkql1dlhqv8px7k81y2l20hhxfgnh2m1")
+             (julia-patch "libunwind-static-arm"
+                          "1jk3bmiw61ypcchqkk1fyg5wh8wpggk574wxyfyaic870zh3lhgq")
+             (julia-patch "libunwind-cfa-rsp"
+                          "1aswjhvysahhldbzh1afbf0hsjxrvs6xidsz2i7s1cjkjbdiia1z"))))))
     (home-page "https://github.com/JuliaLang/tree/master/deps/")))
 
 (define (julia-patch-url version name)

gnu/packages/patches/libunwind-julia-fix-GCC10-fno-common.patch

@@ -0,0 +1,40 @@
+Fix compilation with -fno-common.
+
+Borrowed from upstream 29e17d8d2ccbca07c423e3089a6d5ae8a1c9cb6e.
+Author:     Yichao Yu <yyc1992@gmail.com>
+AuthorDate: Tue Mar 31 00:43:32 2020 -0400
+Commit:     Dave Watson <dade.watson@gmail.com>
+CommitDate: Tue Mar 31 08:06:29 2020 -0700
+
+diff --git a/src/x86/Ginit.c b/src/x86/Ginit.c
+index f6b8dc2..9550efa 100644
+--- a/src/x86/Ginit.c
++++ b/src/x86/Ginit.c
+@@ -54,13 +54,6 @@ tdep_uc_addr (ucontext_t *uc, int reg)
+ 
+ # endif /* UNW_LOCAL_ONLY */
+ 
+-HIDDEN unw_dyn_info_list_t _U_dyn_info_list;
+-
+-/* XXX fix me: there is currently no way to locate the dyn-info list
+-       by a remote unwinder.  On ia64, this is done via a special
+-       unwind-table entry.  Perhaps something similar can be done with
+-       DWARF2 unwind info.  */
+-
+ static void
+ put_unwind_info (unw_addr_space_t as, unw_proc_info_t *proc_info, void *arg)
+ {
+@@ -71,7 +64,12 @@ static int
+ get_dyn_info_list_addr (unw_addr_space_t as, unw_word_t *dyn_info_list_addr,
+                         void *arg)
+ {
+-  *dyn_info_list_addr = (unw_word_t) &_U_dyn_info_list;
++#ifndef UNW_LOCAL_ONLY
++# pragma weak _U_dyn_info_list_addr
++  if (!_U_dyn_info_list_addr)
++    return -UNW_ENOINFO;
++#endif
++  *dyn_info_list_addr = _U_dyn_info_list_addr ();
+   return 0;
+ }
+