Build errors on older clang versions (Wextra-semi-stmt, Wsign-conversion)

[michael-dwan]

Hello, I ran into an admittedly probably small-reaching issue. I'm working on a project on a much older macOS, and have a few versions of clang (AppleClang 13.0.0, and several version of clang 15.0.x from upstream.)

AppleClang 13 seems fine, but, on a couple of the 15.0.x version (15.0.7 for instance), using EXEC_TIME functionality leads to errors from the warnings:

• -Wextra-semi-stmt
• -Wsign-conversion

I've forked the repo to fix it for myself, but, the changes seemed localized enough that I thought I'd see if there was any interest in a pull-request, recognizing that it's probably not an issue for most users.

Change can be previewed here: master...michael-dwan:Unity:fix/Issue-749_build_errors_in_older_clangs

[mvandervoord]

A PR would be much appreciated, actually! That's a good thing to fix.