Bug#835847: gcc-6: rework the patch of gdc cross install directory patch with 6.2.0

[YunQiang Su <wzssyqa@gmail.com>]

Package: src:gcc-6
Version: 6.2.0-1

Hi, 6.2 changes the way to set gdc install directory.
We need rework this patch.

-- 
YunQiang Su

diff --git a/debian/patches/gdc-cross-install-location.diff b/debian/patches/gdc-cross-install-location.diff
index 21d4e92..c4dd439 100644
--- a/debian/patches/gdc-cross-install-location.diff
+++ b/debian/patches/gdc-cross-install-location.diff
@@ -1,13 +1,13 @@
-Index: b/src/libphobos/configure.ac
+Index: b/src/libphobos/m4/druntime.m4
 ===================================================================
---- a/src/libphobos/configure.ac
-+++ b/src/libphobos/configure.ac
-@@ -167,7 +167,7 @@ AC_SUBST(phobos_toolexecdir)
- AC_SUBST(phobos_toolexeclibdir)
+--- a/src/libphobos/m4/druntime.m4
++++ b/src/libphobos/m4/druntime.m4
+@@ -78,7 +78,7 @@ AC_DEFUN([DRUNTIME_INSTALL_DIRECTORIES],
+   AC_SUBST(toolexeclibdir)
  
- # Default case for install directory for D sources files.
--gdc_include_dir='${libdir}/gcc/${target_alias}'/${d_gcc_ver}/include/d
-+gdc_include_dir='${libdir}/gcc-cross/${target_alias}'/${d_gcc_ver}/include/d
- AC_SUBST(gdc_include_dir)
+   # Default case for install directory for D sources files.
+-  gdc_include_dir='${libdir}/gcc/${target_alias}'/${d_gcc_ver}/include/d
++  gdc_include_dir='${libdir}/gcc-cross/${target_alias}'/${d_gcc_ver}/include/d
+   AC_SUBST(gdc_include_dir)
+ ])
  
- dnl Checks for header files.