V3 libstdc++ testsuite problem: warning: -ffunction-sections

[Billinghurst, David (CRTS)]

Have just run dejagnu based libstdc++-v3 testsuite on the branch (on cygwin)
for the first time.  There are a lot of false "excess error" failures due to
warnings like:

FAIL: 17_intro/header_cassert.cc (test for excess errors)
Excess errors:
/usr/local/src/gcc/libstdc++-v3/testsuite/17_intro/header_cassert.cc:0:
warning: -ffunction-sections
   may affect debugging on some targets.