Add cmake support for WOLFSSL_CUSTOM_CURVES

[embhorn]

Description

Add support for the WOLFSSL_CUSTOM_CURVES define in the cmake build.

Fixes zd18558

Testing

mkdir build && cd build
cmake -DWOLFSSL_ECCCUSTCURVES=all ..
cmake --build .
sudo cmake --build . --target install

Build ECC examples in https://github.com/wolfSSL/wolfssl-examples/tree/master/ecc
Then run ecc-verify example and see that Not compiled in... error is not displayed.

Checklist

• added tests
• updated/added doxygen
• updated appropriate READMEs
• Updated manual and documentation

[embhorn]

retest this please

Build [PRB-generic-config-parser #5731](https://cloud.wolfssl-test.com/jenkins/job/PRB-generic-config-parser/5731/) completed: FAILURE
[Pipeline] }
[PRB-generic-config-parser #5731](https://cloud.wolfssl-test.com/jenkins/job/PRB-generic-config-parser/5731/) completed with status FAILURE (propagate: false to ignore)
org.jenkinsci.plugins.workflow.actions.ErrorAction$ErrorId: 254322d1-bcec-464e-a117-64e66ad16278
Setting overall build result to FAILURE
[Pipeline] // catchError
[Pipeline] }

[embhorn]

Customer confirms working