Subzero: Fix lit and cross tests broken in f8b4cc8.

pydir/crosstest.py

 #!/usr/bin/env python2
 
 import argparse
 import os
 import subprocess
 import sys
 import tempfile
 
 from utils import shellcmd
 from utils import FindBaseNaCl
@@ skipping 102 matching lines @@
                   '-externalize',
                   '-filetype=' + args.filetype,
                   '-o=' + (obj_sz if args.filetype == 'obj' else asm_sz),
                   bitcode])
         if args.filetype != 'obj':
             shellcmd(['{bin}/llvm-mc'.format(bin=bindir),
                       '-triple=' + triple,
                       '-filetype=obj',
                       '-o=' + obj_sz,
                       asm_sz])
+        # Each separately translated Subzero object file contains its own
+        # definition of the __Sz_block_profile_info profiling symbol.  Avoid
+        # linker errors (multiply defined symbol) by making all copies weak.
+        # (This could also be done by Subzero if it supported weak symbol
+        # definitions.)  This approach should be OK because cross tests are
+        # currently the only situation where multiple translated files are
+        # linked into the executable, but when PNaCl supports shared nexe
+        # libraries, this would need to change.
+        shellcmd(['objcopy', '--weaken-symbol=__Sz_block_profile_info', obj_sz])
         objs.append(obj_sz)
         if args.crosstest_bitcode:
             shellcmd(['{bin}/pnacl-llc'.format(bin=bindir),
                       '-mtriple=' + triple,
                       # Use sse2 instructions regardless of input -mattr
                       # argument to avoid differences in (undefined) behavior of
                       # converting NaN to int.
                       '-mattr=sse2',
                       '-externalize',
                       '-filetype=obj',
@@ skipping 16 matching lines @@
     sb_native_args = (['-O0', '--pnacl-allow-native', '-arch', 'x8632',
                        '-Wn,-defsym=__Sz_AbsoluteZero=0']
                       if args.sandbox else
                       ['-g', '-m32', '-lm', '-lpthread',
                        '-Wl,--defsym=__Sz_AbsoluteZero=0'])
     shellcmd([compiler, args.driver] + objs +
              ['-o', os.path.join(args.dir, args.output)] + sb_native_args)
 
 if __name__ == '__main__':
     main()