[PATCH] Add symbol checking script to libc++ to detect ABI changes.

[David Majnemer]

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Comment at: util/sym_check/sym_check/extract.py:56
@@ +55,3 @@
+    """
+    out,err,exitCode = util.execute_command_verbose(['nm', '-P', '-g', lib_file])
+    if exitCode != 0:
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IMO, it would be nice if this worked with llvm-nm.

http://reviews.llvm.org/D4946