Ignore whitespace within lines when validating objdump outputs in CI

[austinglaser]

Closes #55

Based at #54

If the output of cargo objdump changes only with regard to whitespace, it's probably OK to still pass CI. Most readers probably won't even notice whitespace differences in the first place.

The diff documentation says of whitespace-suppressing options:

The --ignore-space-change (-b) option is stronger than -E and -Z combined. It ignores white space at line end, and considers all other sequences of one or more white space characters within a line to be equivalent.

This ignores only changes within a line -- changes which span multiple lines (i.e. the addition or removal of whitespace-only lines) will still compare as different. This is a good thing, because there are places the book includes a subset of a file based on line numbers.

[rust-highfive]

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[austinglaser]

Whether this is the right strategy is up for debate, which is why I've opened it as a separate PR from #54

[therealprof]

bors r+

[bors[bot]]

Build succeeded

• continuous-integration/travis-ci/push