brltty: use gcc instead of ld to link shared objects

Bump to version 5.6 has reintroduced the issue fixed by patch 854093 on
version 5.5.

Indeed, third patch was merged upstream but it was then reverted:
https://github.com/brltty/brltty/commit/9e7d62c869d3c1cbe12dda8b0291a4692c193416

Moreover, since commit 3a2e3f6fa5ef0a210ffeba5ed05c79965d0cc3c7, MKOBJ
was renamed into MKREL. So, patch again brltty, overwrite
MKREL to use "gcc -shared -o" instead of "ld -r -o" if gcc is available
(as suggested by Arnout: https://patchwork.ozlabs.org/patch/972614).

Fixes:
 - http://autobuild.buildroot.org/results/31f682838b3d3b2c7103b5c51f2aba0b89d4f630

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

package/brltty/0002-Fix-linking-error-on-mips64el.patch

@@ -0,0 +1,42 @@
+From ddb06335935ef1458fe98f99cdc5d5fe6757fd02 Mon Sep 17 00:00:00 2001
+From: Fabrice Fontaine <fontaine.fabrice@gmail.com>
+Date: Wed, 3 Oct 2018 19:06:40 +0200
+Subject: [PATCH] Fix linking error on mips64el
+
+Patch that was fixing build on mips64el was reverted:
+https://github.com/brltty/brltty/commit/9e7d62c869d3c1cbe12dda8b0291a4692c193416
+
+So fix the issue again, this time by checking if $(GCC) is available as
+suggested by Arnout during review of buildroot patch:
+https://patchwork.ozlabs.org/patch/972614
+
+Fixes:
+ - http://autobuild.buildroot.org/results/31f682838b3d3b2c7103b5c51f2aba0b89d4f630
+
+Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
+[Upstream status: https://github.com/brltty/brltty/pull/149]
+---
+ configure.ac | 7 ++++++-
+ 1 file changed, 6 insertions(+), 1 deletion(-)
+
+diff --git a/configure.ac b/configure.ac
+index 1e2774abf..a488d3d52 100644
+--- a/configure.ac
++++ b/configure.ac
+@@ -481,7 +481,12 @@ AC_CACHE_CHECK([for make relocatable object command], [brltty_cv_prog_make_objec
+ case "${host_os}"
+ in
+    *)
+-      brltty_cv_prog_make_object_relocatable="\$(LD) -r -o"
++      if test "${GCC}" = "yes"
++      then
++         brltty_cv_prog_make_object_relocatable="\$(CC) -shared -o"
++      else
++         brltty_cv_prog_make_object_relocatable="\$(LD) -r -o"
++      fi
+       ;;
+ esac])
+ MKREL="${brltty_cv_prog_make_object_relocatable}"
+-- 
+2.17.1
+