Remove redundant, stale shell fn from build-host-gcc.sh

 get_default_binutils_version_for_gcc is also in dev-defaults.sh
and has now diverged from the one in build-host-gcc.sh
diff --git a/build/tools/build-host-gcc.sh b/build/tools/build-host-gcc.sh
index 2145396..a5a52ab 100755
--- a/build/tools/build-host-gcc.sh
+++ b/build/tools/build-host-gcc.sh
@@ -489,17 +489,6 @@
     fi
 }
 
-get_default_binutils_version_for_gcc ()
-{
-    local RET
-    case $1 in
-        arm-*-4.4.3|x86-*-4.4.3|x86-4.4.3) RET=2.19;;
-        *-4.6) RET=2.21;;
-        *) RET=2.22;;
-    esac
-    echo "$RET"
-}
-
 # Check that a given compiler generates code correctly
 #
 # This is to detect bad/broken toolchains, e.g. amd64-mingw32msvc