math/eispack: fix build on armv7

GNU ld supports neither -z relro nor -z norelro on armv7.
Unfortunately <bsd.lib.mk> insists on adding either to the link.
Work around this issue by using base ld for the link.

MFH: 2025Q2
(cherry picked from commit 4b940a90490f2ec8c0f0108e655abc6f7faac276)