Don't lint build output
Don't lint build output

npm test has been failing if previous build output was present,
because the generated build/msg/??.msg files are missing a trailing
newline and the line to exclude build/* from being linted was
inadvertently omitted from commit 9e72378.

(Much of the rest of the build output would also fail lint checks but
was already excluded by the *_compressed*.js exclusion.)

google/blockly,google/blockly,google/blockly,rachel-fenichel/blockly,mark-friedman/blockly,google/blockly,rachel-fenichel/blockly,mark-friedman/blockly,mark-friedman/blockly,google/blockly,rachel-fenichel/blockly,rachel-fenichel/blockly,rachel-fenichel/blockly,google/blockly,mark-friedman/blockly,mark-friedman/blockly,rachel-fenichel/blockly,mark-friedman/blockly,google/blockly,rachel-fenichel/blockly