gnu: libarchive: Fix several security issues.

* gnu/packages/backup.scm (libarchive)[replacement]: New field.
(libarchive/fixed): New variable.
* gnu/packages/patches/libarchive-7zip-heap-overflow.patch,
gnu/packages/patches/libarchive-fix-symlink-check.patch,
gnu/packages/patches/libarchive-fix-filesystem-attacks.patch,
gnu/packages/patches/libarchive-safe_fprintf-buffer-overflow.patch: New files.
* gnu/local.mk (dist_patch_DATA): Add them.

gnu/packages/backup.scm

@@ -172,6 +172,7 @@ backups (called chunks) to allow easy burning to CD/DVD.")
 (define-public libarchive
   (package
     (name "libarchive")
+    (replacement libarchive/fixed)
     (version "3.2.1")
     (source
      (origin
@@ -227,6 +228,17 @@ archive.  In particular, note that there is currently no built-in support for
 random access nor for in-place modification.")
     (license license:bsd-2)))
 
+(define libarchive/fixed
+  (package
+    (inherit libarchive)
+    (source (origin
+              (inherit (package-source libarchive))
+              (patches (search-patches
+                         "libarchive-7zip-heap-overflow.patch"
+                         "libarchive-fix-symlink-check.patch"
+                         "libarchive-fix-filesystem-attacks.patch"
+                         "libarchive-safe_fprintf-buffer-overflow.patch"))))))
+
 (define-public rdup
   (package
     (name "rdup")