gnu: gcc-4.7: Resurrect building with gcc-5.4.0.

* gnu/packages/patches/gcc-4-compile-with-gcc-5.patch: New file.
* gnu/local.mk (dist_patch_DATA): Add it.
* gnu/packages/gcc.scm (gcc-4.7): Use it.

gnu/local.mk

@@ -11,6 +11,7 @@
 # Copyright © 2016 Ben Woodcroft <donttrustben@gmail.com>
 # Copyright © 2016, 2017 Alex Vong <alexvong1995@gmail.com>
 # Copyright © 2016, 2017 Efraim Flashner <efraim@flashner.co.il>
+# Copyright © 2016, 2017 Jan Nieuwenhuizen <janneke@gnu.org>
 # Copyright © 2017 Tobias Geerinckx-Rice <me@tobias.gr>
 # Copyright © 2017 Clément Lassieur <clement@lassieur.org>
 # Copyright © 2017 Mathieu Othacehe <m.othacehe@gmail.com>
@@ -637,6 +638,7 @@ dist_patch_DATA =						\
   %D%/packages/patches/gcc-cross-environment-variables.patch	\
   %D%/packages/patches/gcc-libvtv-runpath.patch			\
   %D%/packages/patches/gcc-strmov-store-file-names.patch	\
+  %D%/packages/patches/gcc-4-compile-with-gcc-5.patch		 \
   %D%/packages/patches/gcc-4.6-gnu-inline.patch			\
   %D%/packages/patches/gcc-4.9.3-mingw-gthr-default.patch	\
   %D%/packages/patches/gcc-5.0-libvtv-runpath.patch		\

gnu/packages/gcc.scm

@@ -136,6 +136,7 @@ (define-public gcc-4.7
                (method url-fetch)
                (uri (string-append "mirror://gnu/gcc/gcc-"
                                    version "/gcc-" version ".tar.bz2"))
+               (patches (search-patches "gcc-4-compile-with-gcc-5.patch"))
                (sha256
                 (base32
                  "10k2k71kxgay283ylbbhhs51cl55zn2q38vj5pk4k950qdnirrlj"))))

gnu/packages/patches/gcc-4-compile-with-gcc-5.patch

@@ -0,0 +1,65 @@
+Taken from  https://gcc.gnu.org/cgi-bin/get-raw-msg?listname=gcc-patches&date=2016-01&msgid=1451802493-17406-1-git-send-email-vapier%40gentoo.org
+
+Since the 3.0.3 release of gperf (made in May 2007), the generated func
+has had the gnu_inline attribute applied to it.  The gcc source however
+has not been updated to include that which has lead to a mismatch.
+
+In practice, this hasn't been an issue for two reasons:
+(1) Before gcc-5, the default standard was (gnu) C89, and gcc does not
+warn or throw an error in this mode.
+(2) Starting with gcc-4.8, the compiler driver used to build gcc was
+changed to C++, and g++ does not warn or throw an error in this mode.
+
+This error does show up though when using gcc-5 to build gcc-4.7 or
+older as then the default is (gnu) C11 and the C compiler driver is
+used.  That failure looks like:
+In file included from .../gcc-4.7.4/gcc/cp/except.c:990:0:
+cfns.gperf: At top level:
+cfns.gperf:101:1: error: 'gnu_inline' attribute present on 'libc_name_p'
+cfns.gperf:26:14: error: but not here
+
+Whether the compiler should always emit this error regardless of the
+active standard or compiler driver is debatable (I think it should be
+consistent -- either always do it or never do it).
+
+2015-08-06  Mike Frysinger  <vapier@gentoo.org>
+
+	* cfns.gperf [__GNUC__, __GNUC_STDC_INLINE__]: Apply the
+	__gnu_inline__ attribute.
+	* cfns.h: Regenerated.
+---
+ gcc/cp/cfns.gperf | 3 +++
+ gcc/cp/cfns.h     | 3 +++
+ 2 files changed, 6 insertions(+)
+
+diff --git a/gcc/cp/cfns.gperf b/gcc/cp/cfns.gperf
+index 68acd3d..953262f 100644
+--- a/gcc/cp/cfns.gperf
++++ b/gcc/cp/cfns.gperf
+@@ -22,6 +22,9 @@ __inline
+ static unsigned int hash (const char *, unsigned int);
+ #ifdef __GNUC__
+ __inline
++#ifdef __GNUC_STDC_INLINE__
++__attribute__ ((__gnu_inline__))
++#endif
+ #endif
+ const char * libc_name_p (const char *, unsigned int);
+ %}
+diff --git a/gcc/cp/cfns.h b/gcc/cp/cfns.h
+index 1c6665d..6d00c0e 100644
+--- a/gcc/cp/cfns.h
++++ b/gcc/cp/cfns.h
+@@ -53,6 +53,9 @@ __inline
+ static unsigned int hash (const char *, unsigned int);
+ #ifdef __GNUC__
+ __inline
++#ifdef __GNUC_STDC_INLINE__
++__attribute__ ((__gnu_inline__))
++#endif
+ #endif
+ const char * libc_name_p (const char *, unsigned int);
+ /* maximum key range = 391, duplicates = 0 */
+-- 
+2.6.2
+