gnu: mutt: Don't retain reference to GCC.

* gnu/packages/patches/mutt-store-references.patch: New file.
* gnu/packages/mail.scm (mutt)[source]: Use it.
* gnu-system.am (dist_patch_DATA): Add it.

gnu-system.am

@@ -523,6 +523,7 @@ dist_patch_DATA =						\
   gnu/packages/patches/mumps-build-parallelism.patch		\
   gnu/packages/patches/mupdf-buildsystem-fix.patch		\
   gnu/packages/patches/mutt-CVE-2014-9116.patch			\
+  gnu/packages/patches/mutt-store-references.patch		\
   gnu/packages/patches/net-tools-bitrot.patch			\
   gnu/packages/patches/ngircd-handle-zombies.patch		\
   gnu/packages/patches/ngircd-no-dns-in-tests.patch		\

gnu/packages/mail.scm

@@ -184,7 +184,9 @@ aliasing facilities to work just as they would on normal mail.")
              (sha256
               (base32
                "0dzx4qk50pjfsb6cs5jahng96a52k12f7pm0sc78iqdrawg71w1s"))
-             (patches (list (search-patch "mutt-CVE-2014-9116.patch")))))
+             (patches (map search-patch
+                           '("mutt-CVE-2014-9116.patch"
+                             "mutt-store-references.patch")))))
     (build-system gnu-build-system)
     (inputs
      `(("cyrus-sasl" ,cyrus-sasl)

gnu/packages/patches/mutt-store-references.patch

@@ -0,0 +1,16 @@
+By default 'mutt' embeds configure flags and the output of 'gcc -v',
+which contains the store file name of Bash and GCC.  This patch makes
+sure we don't embed a reference to these in 'mutt'.
+
+--- mutt-1.5.23/txt2c.sh	2015-06-26 22:56:56.500731643 +0200
++++ mutt-1.5.23/txt2c.sh	2015-06-26 22:57:26.664583900 +0200
+@@ -21,6 +21,8 @@ txt2c_fallback () {
+ 	echo ";"
+ }
+ 
++echo "unsigned char $1[] = \"value of '$1' not kept\";"
++exit 0
+ ./txt2c test </dev/null >/dev/null 2>&1 &&
+ ./txt2c "$1" ||
+ txt2c_fallback "$1"
+