Fix aarch64 compilation issues

[jwidauer]

Changes in this pull request

Changes some specific variables from an i8 to a c_char, since the functions that use these variables take c_chars as input.
This is specifically an issue when trying to cross compile for aarch64, since c_char is defined as a u8 for that architecture.

Checklist

• This PR represents a single feature, fix, or change.
• All applicable changes have been documented.
• Any TO DO items (or similar) have been entered as GitHub issues and the link to that issue has been included in a comment.

[scouten-adobe]

@jwidauer thank you for drawing this issue to our attention and submitting a fix. I'd like to ensure that we don't lose this change over time. Any chance you could suggest a GitHub Actions enhancement that shows the previous code failing on aarch64 and then shows this PR passing that test?

[codecov]

Codecov Report

Merging #159 (7a2cdb1) into main (f97147e) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##             main     #159   +/-   ##
=======================================
  Coverage   97.87%   97.87%           
=======================================
  Files           8        8           
  Lines        1504     1504           
=======================================
  Hits         1472     1472           
  Misses         32       32           

Impacted Files	Coverage Δ
src/xmp_iterator.rs	100.00% <100.00%> (ø)
src/xmp_meta.rs	99.80% <100.00%> (ø)

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[jwidauer]

@scouten-adobe Thanks for your quick reply!
I added another step to the github actions workflow, which uses cross to check the cross compilation to aarch64-unknown-linux-gnu. It should also be pretty easy to extend it to check more architectures as well.
Is this similar to what you had in mind?

[jwidauer]

@scouten-adobe Were you able to already have a look at the proposed changes to the CI? What do you think?

[scouten-adobe]

@jwidauer was on vacation late last week; looking at it now.

[scouten-adobe]

Confirmed via #160 that the CI changes as proposed do detect the failure and that this version succeeds.

Fixing code format in xmp_iterator and then I will merge. Thank you!

[scouten-adobe]

Looks great. Thank you!

[jwidauer]

@scouten-adobe Thanks for the quick responses! Happy this got in! 😄