gnu: efibootmgr: Update to 17.

* gnu/packages/linux.scm (efibootmgr): Update to 17.
[source]: Use GIT-FETCH and GIT-FILE-NAME.
Add a patch to build against efivar@37.
* gnu/packages/patches/efibootmgr-remove-extra-decl.patch: New file.
* gnu/local.mk (dist_patch_DATA): Add it.

gnu/packages/patches/efibootmgr-remove-extra-decl.patch

@@ -0,0 +1,27 @@
+From 99b578501643377e0b1994b2a068b790d189d5ad Mon Sep 17 00:00:00 2001
+From: Peter Jones <pjones@redhat.com>
+Date: Wed, 13 Jun 2018 09:41:01 -0400
+Subject: [PATCH] remove extra decl
+
+Signed-off-by: Peter Jones <pjones@redhat.com>
+---
+ src/efibootmgr.c | 3 ---
+ 1 file changed, 3 deletions(-)
+
+diff --git a/src/efibootmgr.c b/src/efibootmgr.c
+index de38f01..4e1a680 100644
+--- a/src/efibootmgr.c
++++ b/src/efibootmgr.c
+@@ -1536,9 +1536,6 @@ parse_opts(int argc, char **argv)
+ 					       "invalid numeric value %s\n",
+ 					       optarg);
+ 			}
+-                        /* XXX efivar-36 accidentally doesn't have a public
+-                         * header for this */
+-			extern int efi_set_verbose(int verbosity, FILE *errlog);
+ 			efi_set_verbose(opts.verbose - 2, stderr);
+ 			break;
+ 		case 'V':
+-- 
+2.24.0
+