Build log attached. This appears to be a straightforward coding typo. In source file dbdimp.c, a local utility function print_embedded_options() is called with three parameters but the function prototype has only two. Most straightforward solution is to add the missing parameter. Patch and modified ebuild attached. This compile error only manifests of the embedded USE flag is set. Also, as the latest upstream (4.32) still appears to have this issue, I will also be submitting to upstream.
Created attachment 411764 [details] Build log. Build log attached.
Created attachment 411766 [details, diff] Patch to add the missing parameter support.
Created attachment 411768 [details] Modified ebuild applies the patch.
Created attachment 411770 [details] emerge --info '=dev-perl/DBD-mysql-4.31.0::gentoo'
Bumped && fixed https://gitweb.gentoo.org/repo/gentoo.git/commit/?id=f2b6b0f0106efe89395009da132bca115984dfd7