gitian: fix x86_64 build with static libstdc++

contrib/gitian-descriptors/gitian-linux.yml

@@ -15,6 +15,7 @@ packages:
 - "faketime"
 - "bsdmainutils"
 - "binutils-gold"
+- "libstdc++6-4.6-pic"
 reference_datetime: "2013-06-01 00:00:00"
 remotes:
 - "url": "https://github.com/bitcoin/bitcoin.git"
@@ -69,6 +70,14 @@ script: |
     make ${MAKEOPTS} -C ${BASEPREFIX} HOST="${i}"
   done
 
+  # Ubuntu precise hack: Not an issue in later versions.
+  # Precise's libstdc++.a is non-pic. There's an optional libstdc++6-4.6-pic
+  #   package which provides libstdc++_pic.a, but the linker can't find it.
+  # Symlink it to a path that will be included in our link-line so that the
+  # linker picks it up before the default libstdc++.a.
+  # This is only necessary for 64bit.
+  ln -s /usr/lib/gcc/x86_64-linux-gnu/4.6/libstdc++_pic.a ${BASEPREFIX}/x86_64-unknown-linux-gnu/lib/libstdc++.a
+
   # Create the release tarball using (arbitrarily) the first host
   ./autogen.sh
   ./configure --prefix=${BASEPREFIX}/`echo "${HOSTS}" | awk '{print $1;}'`