binutils-cross: install non-prefixed links for gcc

This will install, for example, a 'ld.gold' symlink in
STAGING_BINDIR_TOOLCHAIN/gcc, which we can then allow gcc to get to.
This makes it possible to rebuild just binutils-cross and use everything
else from an external toolchain, which can be useful to get ahold of
ld.gold when the external toolchain doesn't provide it.

Signed-off-by: Christopher Larson <chris_larson@mentor.com>

core/recipes-devtools/binutils/binutils-cross_%.bbappend

@@ -0,0 +1,6 @@
+do_install_append () {
+    install -d ${D}${bindir}/gcc
+    for i in ${D}${bindir}/${TARGET_PREFIX}*; do
+        ln -s ../$(basename "$i") ${D}${bindir}/gcc/${i##*/${TARGET_PREFIX}}
+    done
+}