grub: add a fix for unused variable in gnulib

This changes adds a fix for an unused variable issue in gnulib.
It is a part of a security series [1].

[1] https://lists.gnu.org/archive/html/grub-devel/2021-03/msg00007.html

(From OE-Core rev: 30cf1e62b0f139cd6e1e3d5c09b7156acfb276b5)

Signed-off-by: Marta Rybczynska <marta.rybczynska@huawei.com>
Signed-off-by: Steve Sakoman <steve@sakoman.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/recipes-bsp/grub/files/0008-gnulib-regexec-Resolve-unused-variable.patch

@@ -0,0 +1,59 @@
+From 9d36bce5d516b6379ba3a0dd1a94a9c035838827 Mon Sep 17 00:00:00 2001
+From: Darren Kenny <darren.kenny@oracle.com>
+Date: Wed, 21 Oct 2020 14:41:27 +0000
+Subject: [PATCH] gnulib/regexec: Resolve unused variable
+
+This is a really minor issue where a variable is being assigned to but
+not checked before it is overwritten again.
+
+The reason for this issue is that we are not building with DEBUG set and
+this in turn means that the assert() that reads the value of the
+variable match_last is being processed out.
+
+The solution, move the assignment to match_last in to an ifdef DEBUG too.
+
+Fixes: CID 292459
+
+Signed-off-by: Darren Kenny <darren.kenny@oracle.com>
+Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
+
+Upstream-Status: Backport [https://git.savannah.gnu.org/cgit/grub.git/commit/?id=a983d36bd9178d377d2072fd4b11c635fdc404b4]
+Signed-off-by: Marta Rybczynska <marta.rybczynska@huawei.com>
+---
+ conf/Makefile.extra-dist                           |  1 +
+ .../lib/gnulib-patches/fix-unused-value.patch      | 14 ++++++++++++++
+ 2 files changed, 15 insertions(+)
+ create mode 100644 grub-core/lib/gnulib-patches/fix-unused-value.patch
+
+diff --git a/conf/Makefile.extra-dist b/conf/Makefile.extra-dist
+index 46c4e95..9b01152 100644
+--- a/conf/Makefile.extra-dist
++++ b/conf/Makefile.extra-dist
+@@ -29,6 +29,7 @@ EXTRA_DIST += grub-core/genemuinit.sh
+ EXTRA_DIST += grub-core/genemuinitheader.sh
+ 
+ EXTRA_DIST += grub-core/lib/gnulib-patches/fix-null-deref.patch
++EXTRA_DIST += grub-core/lib/gnulib-patches/fix-unused-value.patch
+ EXTRA_DIST += grub-core/lib/gnulib-patches/fix-width.patch
+ EXTRA_DIST += grub-core/lib/gnulib-patches/no-abort.patch
+ 
+diff --git a/grub-core/lib/gnulib-patches/fix-unused-value.patch b/grub-core/lib/gnulib-patches/fix-unused-value.patch
+new file mode 100644
+index 0000000..ba51f1b
+--- /dev/null
++++ b/grub-core/lib/gnulib-patches/fix-unused-value.patch
+@@ -0,0 +1,14 @@
++--- a/lib/regexec.c	2020-10-21 14:25:35.310195912 +0000
+++++ b/lib/regexec.c	2020-10-21 14:32:07.961765604 +0000
++@@ -828,7 +828,11 @@
++ 		    break;
++ 		  if (__glibc_unlikely (err != REG_NOMATCH))
++ 		    goto free_return;
+++#ifdef DEBUG
+++		  /* Only used for assertion below when DEBUG is set, otherwise
+++		     it will be over-written when we loop around.  */
++ 		  match_last = -1;
+++#endif
++ 		}
++ 	      else
++ 		break; /* We found a match.  */

meta/recipes-bsp/grub/grub2.inc

@@ -54,6 +54,7 @@ SRC_URI = "${GNU_MIRROR}/grub/grub-${PV}.tar.gz \
            file://0005-efi-Fix-some-malformed-device-path-arithmetic-errors.patch \
            file://0006-kern-efi-Fix-memory-leak-on-failure.patch \
            file://0007-kern-efi-mm-Fix-possible-NULL-pointer-dereference.patch \
+           file://0008-gnulib-regexec-Resolve-unused-variable.patch \
            "
 SRC_URI[md5sum] = "5ce674ca6b2612d8939b9e6abed32934"
 SRC_URI[sha256sum] = "f10c85ae3e204dbaec39ae22fa3c5e99f0665417e91c2cb49b7e5031658ba6ea"