Make a copy of the build you have now and place it in a different area of your hard drive. I save a copy of EL on a different hard drive just in case of emergencies. You can place a backup or test copy outside of the program files.
the same procedure like padawan, i just rename the lastest build then place it into ..lib so when i found some problem just copy the last build into ..lib.
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that's what i usually do as well