gnu: ghostscript: Add $libdir to the RUNPATH of executables.

Fixes <http://bugs.gnu.org/20050>.
Reported by taylanbayirli@gmail.com (Taylan Ulrich Bayırlı/Kammer).

* gnu/packages/patches/ghostscript-runpath.patch: New file.
* gnu/packages/ghostscript.scm (ghostscript)[source]: Use it.
* gnu-system.am (dist_patch_DATA): Add it.

gnu-system.am

@@ -412,6 +412,7 @@ dist_patch_DATA =						\
   gnu/packages/patches/flex-bison-tests.patch			\
   gnu/packages/patches/gawk-shell.patch				\
   gnu/packages/patches/gcc-cross-environment-variables.patch	\
+  gnu/packages/patches/ghostscript-runpath.patch		\
   gnu/packages/patches/glib-tests-desktop.patch			\
   gnu/packages/patches/glib-tests-homedir.patch			\
   gnu/packages/patches/glib-tests-prlimit.patch			\

gnu/packages/ghostscript.scm

@@ -126,8 +126,10 @@ (define-public ghostscript
             (method url-fetch)
             (uri (string-append "mirror://gnu/ghostscript/gnu-ghostscript-"
                                 version ".tar.xz"))
-            (sha256 (base32
-                     "0q4jj41p0qbr4mgcc9q78f5zs8cm1g57wgryhsm2yq4lfslm3ib1"))))
+            (sha256
+             (base32
+              "0q4jj41p0qbr4mgcc9q78f5zs8cm1g57wgryhsm2yq4lfslm3ib1"))
+            (patches (list (search-patch "ghostscript-runpath.patch")))))
    (build-system gnu-build-system)
    (inputs `(("freetype" ,freetype)
              ("lcms" ,lcms)

gnu/packages/patches/ghostscript-runpath.patch

+This patch adds $(libdir) to the RUNPATH of 'gsc' and 'gsx'.
+
+--- gnu-ghostscript-9.14.0/base/unix-dll.mak	2015-04-05 15:12:45.386957927 +0200
++++ gnu-ghostscript-9.14.0/base/unix-dll.mak	2015-04-05 15:12:49.222982359 +0200
+@@ -91,11 +91,11 @@ $(GS_SO_MAJOR): $(GS_SO_MAJOR_MINOR)
+ # Build the small Ghostscript loaders, with Gtk+ and without
+ $(GSSOC_XE): $(GS_SO) $(PSSRC)$(SOC_LOADER)
+ 	$(GLCC) -g -o $(GSSOC_XE) $(PSSRC)dxmainc.c \
+-	-L$(BINDIR) -l$(GS_SO_BASE)
++	-L$(BINDIR) -l$(GS_SO_BASE) -Wl,-rpath=$(libdir)
+ 
+ $(GSSOX_XE): $(GS_SO) $(PSSRC)$(SOC_LOADER)
+ 	$(GLCC) -g $(SOC_CFLAGS) -o $(GSSOX_XE) $(PSSRC)$(SOC_LOADER) \
+-	-L$(BINDIR) -l$(GS_SO_BASE) $(SOC_LIBS)
++	-L$(BINDIR) -l$(GS_SO_BASE) $(SOC_LIBS) -Wl,-rpath=$(libdir)
+ 
+ # ------------------------- Recursive make targets ------------------------- #