this is not discovered during build, but instead just leads to a runtime error. (the installation succeeds despite the error)
That's a bit exotic, and would indicate that the declarations are still present in the <nettle/ecc-curve.h> header file.
Potentially fixed in git for Pike 8.0 and 8.1.
To make binary exports work better, perhaps we should just disable these curves by default and require configure option to enable them?