Gentoo's and upstream gccs don't install _nano variants of stdc++ and supc++.

Let's not refer to them in nano specs of newlib until we do
(or better yet upstream does) have these libraries.

Reported-by: David Flogeras
Bug: https://bugs.gentoo.org/723756
--- a/libgloss/arc/nano.specs
+++ b/libgloss/arc/nano.specs
@@ -11,7 +11,7 @@
 %(nano_link_gcc_c_sequence) --start-group %G %(nano_libc) %(nano_libgloss) --end-group
 
 *link:
-%(nano_link) %:replace-outfile(-lc -lc_nano) %:replace-outfile(-lg -lg_nano) %:replace-outfile(-lstdc++ -lstdc++_nano) %:replace-outfile(-lsupc++ -lsupc++_nano)
+%(nano_link) %:replace-outfile(-lc -lc_nano) %:replace-outfile(-lg -lg_nano)
 
 *lib:
 %{!shared:%{g*:-lg_nano} %{!p:%{!pg:-lc_nano}}%{p:-lc_p}%{pg:-lc_p}}
--- a/libgloss/arm/elf-nano.specs
+++ b/libgloss/arm/elf-nano.specs
@@ -15,7 +15,7 @@
 %(nano_link_gcc_c_sequence) --start-group %G %(nano_libc) %(nano_libgloss) --end-group
 
 *link:
-%(nano_link) %:replace-outfile(-lc -lc_nano) %:replace-outfile(-lg -lg_nano) %:replace-outfile(-lrdimon -lrdimon_nano) %:replace-outfile(-lstdc++ -lstdc++_nano) %:replace-outfile(-lsupc++ -lsupc++_nano)
+%(nano_link) %:replace-outfile(-lc -lc_nano) %:replace-outfile(-lg -lg_nano) %:replace-outfile(-lrdimon -lrdimon_nano)
 
 *lib:
 %{!shared:%{g*:-lg_nano} %{!p:%{!pg:-lc_nano}}%{p:-lc_p}%{pg:-lc_p}}