Eliminate more symbols multiply defined between libsupc++ and libc++.

The remaining multiple definitions were flushed out by attempting to
link libsupc++ and libc++ into the same executable with --whole-archive,
e.g.

clang++ -I../llvm/projects/libcxx/include -nodefaultlibs -Wl,--whole-archive lib/libc++.a /usr/lib/gcc/x86_64-linux-gnu/4.6/libsupc++.a -Wl,--no-whole-archive -lgcc -lgcc_s -lc -lpthread -lrt

(The same technique was used to flush out multiple definitions in
libstdc++.)

Differential Revision: http://llvm-reviews.chandlerc.com/D1824

llvm-svn: 192074
Cr-Mirrored-From: sso://chromium.googlesource.com/_direct/external/github.com/llvm/llvm-project
Cr-Mirrored-Commit: 926aa5f4f24a2e34dfe8dcbe3875550e6e87f70c
diff --git a/src/exception.cpp b/src/exception.cpp
index dc6d049..3e3d40e 100644
--- a/src/exception.cpp
+++ b/src/exception.cpp
@@ -213,10 +213,14 @@
 {
 }
 
+#if !defined(__GLIBCXX__)
+
 nested_exception::~nested_exception() _NOEXCEPT
 {
 }
 
+#endif
+
 _LIBCPP_NORETURN
 void
 nested_exception::rethrow_nested() const