Switch the binutils instructions from trunk to 2.24

I guess I had gotten those instructions from somewhere,
that said to just clone from trunk.
I ran into an issue installing gold through the instructions
and thought it might have been that, but I think it was the
bison issue I mention now in the instructions.
Probably better to leave it at a real release instead of tracking
trunk and having every run of the Pyston install giving a different
output.

docs/INSTALLING.md

@@ -143,13 +143,16 @@ gold is highly recommended as a faster linker.  Pyston contains build-system sup
 
 ```
 cd ~/pyston_deps
-git clone --depth 1 git://sourceware.org/git/binutils-gdb.git binutils
-mkdir binutils-build
-cd binutils-build
-../binutils/configure --enable-gold --enable-plugins --disable-werror
-make all-gold
+wget http://ftp.gnu.org/gnu/binutils/binutils-2.24.tar.gz
+tar xvf binutils-2.24.tar.gz
+mkdir binutils-2.24-build
+cd binutils-2.24-build
+../binutils-2.24/configure --enable-gold --enable-plugins --disable-werror
+make all-gold -j4
 ```
 
+If that last step fails due to complaints about YYSTYPE, try upgrading or installing bison (`sudo apt-get install bison`), removing the binutils-2.24-build directory, and configure + make again.
+
 ### perf
 The `perf` tool is the best way we've found to profile JIT'd code; you can find more details in docs/PROFILING.
 

tools/build_system/ld

@@ -5,12 +5,16 @@ set -eu
 FLAGS=
 RETRY=
 
-if which gold > /dev/null ; then
-    LD=gold
+if [ -f $HOME/pyston_deps/binutils-build/gold/ld-new ]; then
+    LD=$HOME/pyston_deps/binutils-build/gold/ld-new
     # FLAGS="--incremental --incremental-patch=10"
     # RETRY=y
-elif [ -f $HOME/pyston_deps/binutils-build/gold/ld-new ]; then
-    LD=$HOME/pyston_deps/binutils-build/gold/ld-new
+elif [ -f $HOME/pyston_deps/binutils-2.24-build/gold/ld-new ]; then
+    LD=$HOME/pyston_deps/binutils-2.24-build/gold/ld-new
+    # FLAGS="--incremental --incremental-patch=10"
+    # RETRY=y
+elif which gold > /dev/null ; then
+    LD=gold
     # FLAGS="--incremental --incremental-patch=10"
     # RETRY=y
 else