Remove unused variable siz

[purplearmadillo77]

When compiling opam (most recent git) with GCC 11.3.0 on Cygwin64, I get the following error when developer mode is enabled (and NOT during normal compilation since -Werror is only activated in developer mode):

File "src/stubs/libacl/dune", line 12, characters 19-26:
12 |     (names         opamACL)
                        ^^^^^^^
opamACL.c: In function ‘OPAM_get_acl_executable_info’:
opamACL.c:44:12: error: unused variable ‘siz’ [-Werror=unused-variable]
   44 |     size_t siz;
      |            ^~~
cc1: all warnings being treated as errors
make: *** [Makefile:144: build-opam] Error 1

It doesn’t seem like the siz variable is used at all in this file, so I’ve removed it.

Additionally, I wasn't sure which category this would fall under in the changes file - I've currently put it under "Build" since the above was a building problem.

[dra27]

Thanks! Section for master_changes is just fine - would you be able to re-push with the PR number?

[kit-ty-kate]

Thanks! Section for master_changes is just fine - would you be able to re-push with the PR number?

I've done it for them. It's easier and faster this way.

[purplearmadillo77]

Thank you! I'll add the PR number in the future.

[kit-ty-kate]

Thanks