gnu: commencement: Use GMP 6.0.0a for bootstrapping.

* gnu/packages/multiprecision.scm (gmp-6.0): New variable.
* gnu/packages/commencement.scm (gcc-boot0, gcc-final): Use it.
* gnu/packages/patches/gmp-arm-asm-nothumb.patch: New file, reinstated
from before e414a7d.
* gnu-system.am (dist_patch_DATA): Add it.

gnu-system.am

@@ -491,6 +491,7 @@ dist_patch_DATA =						\
   gnu/packages/patches/glibc-locale-incompatibility.patch	\
   gnu/packages/patches/glibc-o-largefile.patch			\
   gnu/packages/patches/glibc-versioned-locpath.patch		\
+  gnu/packages/patches/gmp-arm-asm-nothumb.patch		\
   gnu/packages/patches/gmp-faulty-test.patch			\
   gnu/packages/patches/gnucash-price-quotes-perl.patch		\
   gnu/packages/patches/gnutls-doc-fix.patch			\

gnu/packages/commencement.scm

@@ -231,7 +231,7 @@ (define gcc-boot0
                                         (package-full-name lib)
                                         char-set:letter)
                                       ,(package-name lib)))
-                          (list gmp mpfr mpc))))
+                          (list gmp-6.0 mpfr mpc))))
                (alist-cons-after
                 'install 'symlink-libgcc_eh
                 (lambda* (#:key outputs #:allow-other-keys)
@@ -245,7 +245,7 @@ (define gcc-boot0
                       (symlink "libgcc.a" "libgcc_eh.a"))))
                 ,phases))))))
 
-     (inputs `(("gmp-source" ,(package-source gmp))
+     (inputs `(("gmp-source" ,(package-source gmp-6.0))
                ("mpfr-source" ,(package-source mpfr))
                ("mpc-source" ,(package-source mpc))
                ("binutils-cross" ,binutils-boot0)
@@ -636,7 +636,7 @@ (define gcc-final
                      ("static-bash" ,static-bash-for-glibc)
                      ,@(package-native-inputs gcc-boot0)))
 
-    (inputs `(("gmp-source" ,(bootstrap-origin (package-source gmp)))
+    (inputs `(("gmp-source" ,(bootstrap-origin (package-source gmp-6.0)))
               ("mpfr-source" ,(package-source mpfr))
               ("mpc-source" ,(package-source mpc))
               ("ld-wrapper" ,ld-wrapper-boot3)

gnu/packages/multiprecision.scm

@@ -60,6 +60,24 @@ (define-public gmp
    (license lgpl3+)
    (home-page "http://gmplib.org/")))
 
+(define-public gmp-6.0
+  ;; We keep this one around to bootstrap GCC, to work around a compilation
+  ;; issue on ARM.  See
+  ;; <https://gmplib.org/list-archives/gmp-bugs/2015-December/003848.html>.
+  (package
+    (inherit gmp)
+    (version "6.0.0a")
+    (source (origin
+              (method url-fetch)
+              (uri (string-append "mirror://gnu/gmp/gmp-"
+                                  version ".tar.xz"))
+              (sha256
+               (base32
+                "0r5pp27cy7ch3dg5v0rsny8bib1zfvrza6027g2mp5f6v8pd6mli"))
+              (patches (map search-patch
+                            '("gmp-arm-asm-nothumb.patch"
+                              "gmp-faulty-test.patch")))))))
+
 (define-public mpfr
   (package
    (name "mpfr")

gnu/packages/patches/gmp-arm-asm-nothumb.patch

@@ -0,0 +1,21 @@
+
+# HG changeset patch
+# User Torbjorn Granlund <tege@gmplib.org>
+# Date 1396602422 -7200
+# Node ID 676e2d0f0e4dd301a7066079d2c9326c25c34a40
+# Parent  0194a75b56b21a9196626430af86c5bd9110c42d
+Conditionalise ARM asm on !__thumb__.
+
+diff -r 0194a75b56b2 -r 676e2d0f0e4d mpn/generic/div_qr_1n_pi1.c
+--- a/mpn/generic/div_qr_1n_pi1.c	Thu Apr 03 23:58:51 2014 +0200
++++ b/mpn/generic/div_qr_1n_pi1.c	Fri Apr 04 11:07:02 2014 +0200
+@@ -130,7 +130,7 @@
+ 	     "%2" ((UDItype)(a0)), "r" ((UDItype)(b0)) __CLOBBER_CC)
+ #endif
+ 
+-#if defined (__arm__) && W_TYPE_SIZE == 32
++#if defined (__arm__) && !defined (__thumb__) && W_TYPE_SIZE == 32
+ #define add_mssaaaa(m, sh, sl, ah, al, bh, bl)				\
+   __asm__ (  "adds	%2, %5, %6\n\t"					\
+ 	     "adcs	%1, %3, %4\n\t"					\
+