The configure file tests the version using non-BRE (Basic Regular Expression) \+ tokens, causing it not to match with OpenBSD's grep. Extracting the relevant log output during the cargo build execution:

configure:8265: error: 5.3.0-1-ge13ca993e8ccb9ba9847cc330696e02839f328f7 does not match <major>.<minor>.<bugfix>-<nrev>-g<gid> or VERSION                                                                                          

The grep on line 8259 needs to use actual BRE (just using the * and doubling up the previous atom to require one or more):

echo "${with_version}" | grep '^[0-9][0-9]*\.[0-9][0-9]*\.[0-9][0-9]*-[0-9][0-9]*-g[0-9a-f][0-9a-f]*$'

or (possibly less-portably) you could use -E for Extended Regular Expressions and just + (not \+) such as

echo "${with_version}" | grep -E '^[0-9]+\.[0-9]+\.[0-9]+-[0-9]+-g[0-9a-f]+$'