gnu: gcc: Add $libdir to the RUNPATH of libvtv.so.

* gnu/packages/gcc.scm (gcc-4.9): Inherit from GCC-4.8.
  [source]: Add 'gcc-libvtv-runpath.patch'.
  (gcc-5.1): Inherit from GCC-4.9.
  [source]: Use patches from GCC-4.9.
* gnu/packages/patches/gcc-libvtv-runpath.patch: New file.
* gnu-system.am (dist_patch_DATA): Add it.

gnu-system.am

@@ -420,6 +420,7 @@ dist_patch_DATA =						\
   gnu/packages/patches/gawk-shell.patch				\
   gnu/packages/patches/gcc-arm-link-spec-fix.patch		\
   gnu/packages/patches/gcc-cross-environment-variables.patch	\
+  gnu/packages/patches/gcc-libvtv-runpath.patch			\
   gnu/packages/patches/geoclue-config.patch			\
   gnu/packages/patches/ghostscript-runpath.patch		\
   gnu/packages/patches/gitolite-openssh-6.8-compat.patch	\

gnu/packages/gcc.scm

@@ -316,7 +316,7 @@ Go.  It also includes runtime support libraries for these languages.")
               (patches (list (search-patch "gcc-arm-link-spec-fix.patch")))))))
 
 (define-public gcc-4.9
-  (package (inherit gcc-4.7)
+  (package (inherit gcc-4.8)
     (version "4.9.2")
     (source (origin
               (method url-fetch)
@@ -325,10 +325,12 @@ Go.  It also includes runtime support libraries for these languages.")
               (sha256
                (base32
                 "1pbjp4blk2ycaa6r3jmw4ky5f1s9ji3klbqgv8zs2sl5jn1cj810"))
-             (patches (list (search-patch "gcc-arm-link-spec-fix.patch")))))))
+              (patches (map search-patch
+                            '("gcc-arm-link-spec-fix.patch"
+                              "gcc-libvtv-runpath.patch")))))))
 
 (define-public gcc-5.1
-  (package (inherit gcc-4.7)
+  (package (inherit gcc-4.9)
     (version "5.1.0")
     (source (origin
               (method url-fetch)
@@ -337,7 +339,7 @@ Go.  It also includes runtime support libraries for these languages.")
               (sha256
                (base32
                 "1bd5vj4px3s8nlakbgrh38ynxq4s654m6nxz7lrj03mvkkwgvnmp"))
-             (patches (list (search-patch "gcc-arm-link-spec-fix.patch")))))))
+              (patches (origin-patches (package-source gcc-4.9)))))))
 
 (define* (custom-gcc gcc name languages #:key (separate-lib-output? #t))
   "Return a custom version of GCC that supports LANGUAGES."

gnu/packages/patches/gcc-libvtv-runpath.patch

@@ -0,0 +1,15 @@
+GCC 4.9 and later have libvtv and, just like libstdc++ (see
+https://gcc.gnu.org/bugzilla/show_bug.cgi?id=32354), it doesn't
+have $libdir in its RUNPATH, but it NEEDs libgcc_s.  This patch
+fixes that.
+
+--- gcc-4.9.2/libvtv/Makefile.in	2014-10-30 09:28:58.000000000 +0100
++++ gcc-4.9.2/libvtv/Makefile.in	2015-04-30 09:51:04.161129705 +0200
+@@ -15,6 +15,7 @@
+ 
+ @SET_MAKE@
+ 
++AM_LDFLAGS = -Wl,-rpath=$(libdir)
+ 
+ VPATH = @srcdir@
+ pkgdatadir = $(datadir)/@PACKAGE@