guix: repro: Sort find output in libtool for gcc-8

Otherwise the resulting .a static libraries (e.g. libstdc++.a) will not
be reproducible and end up making the Bitcoin binaries non-reproducible
as well.

See: https://reproducible-builds.org/docs/archives/#gnu-libtool

Author: dongcarl

contrib/guix/manifest.scm

@@ -130,12 +130,16 @@ chain for " target " development."))
       (home-page (package-home-page xgcc))
       (license (package-license xgcc)))))
 
+(define base-gcc
+  (package-with-extra-patches gcc-8
+    (search-our-patches "gcc-8-sort-libtool-find-output.patch")))
+
 (define* (make-bitcoin-cross-toolchain target
                                        #:key
                                        (base-gcc-for-libc gcc-7)
                                        (base-kernel-headers linux-libre-headers-5.4)
                                        (base-libc glibc)  ; glibc 2.31
-                                       (base-gcc (make-gcc-rpath-link gcc-8)))
+                                       (base-gcc (make-gcc-rpath-link base-gcc)))
   "Convenience wrapper around MAKE-CROSS-TOOLCHAIN with default values
 desirable for building Bitcoin Core release binaries."
   (make-cross-toolchain target
@@ -153,7 +157,7 @@ desirable for building Bitcoin Core release binaries."
          (pthreads-xlibc mingw-w64-x86_64-winpthreads)
          (pthreads-xgcc (make-gcc-with-pthreads
                          (cross-gcc target
-                                    #:xgcc (make-ssp-fixed-gcc gcc-8)
+                                    #:xgcc (make-ssp-fixed-gcc base-gcc)
                                     #:xbinutils xbinutils
                                     #:libc pthreads-xlibc))))
     ;; Define a meta-package that propagates the resulting XBINUTILS, XLIBC, and