[REG] Fixed Build failure when sometimes command output contain SOFT HYPHEN(0xad)

[REG] Fixed Build failure when command output contain SOFT HYPHEN(0xad)
    
Change "decode([encoding])" to "decode([encoding], [errors='replace'])" to  make sure 0xad (usaully on Windows) don't cause error when decoding.
    
BUG=https://crosswalk-project.org/jira/browse/XWALK-2468