[AIX] Include symbol alias in extract_symbols.py

nm does not show size for aliased symbols,
we should still extract them if they are external.

Reviewed By: hubert.reinterpretcast

Differential Revision: https://reviews.llvm.org/D107112

Author: Jinsong Ji

llvm/utils/extract_symbols.py

@@ -53,7 +53,12 @@ def nm_get_symbols(lib):
     process.stdin.close()
     for line in process.stdout:
         # Look for external symbols that are defined in some section
-        match = re.match("^(\S+)\s+[BDGRSTVW]\s+\S+\s+\S+$", line)
+        # The POSIX format is:
+        #   name   type   value   size
+        # The -P flag displays the size field for symbols only when applicable,
+        # so the last field is optional. There's no space after the value field,
+        # but \s+ match newline also, so \s+\S* will match the optional size field.
+        match = re.match("^(\S+)\s+[BDGRSTVW]\s+\S+\s+\S*$", line)
         if match:
             yield match.group(1)
     process.wait()