devel/pructl: fix link by adding -lBlocksRuntime

PR: 269268
MFH: 2023Q1
Approved by: maintainer timeout (2 weeks)
Approved by: flo (mentor)
Differential Revision: https://reviews.freebsd.org/D38623

(cherry picked from commit 82afcc13ccae2d8573525d3a44f7d87d8d2a6bfe)