Allow short "moxiebox" alias

... while making use of the new tunables.

Also, unmark the moxie-elf as broken: the ld scripts installed by newlib
can be found by the compiler and can link the binaries. Why the default
script is broken is not ct-ng's problem...

Signed-off-by: Alexey Neyman <stilor@att.net>

config/libc/moxiebox.in

@@ -15,3 +15,13 @@
 ## select LIBELF_NEEDED
 ##
 ## help Secure execution runtime for Moxie architecture.
+
+config MOXIEBOX_SHORT_TUPLE
+    bool "Use 'moxiebox-' as target tuple"
+    select OMIT_TARGET_ARCH
+    select OMIT_TARGET_VENDOR
+    select TARGET_SKIP_CONFIG_SUB
+    help
+      Moxiebox refers to the tools configured for 'moxie-unknown-moxiebox-' by
+      a short, 'moxiebox-' prefix. Though non-canonical, it seems to be officially
+      endorsed.