Enable MSCHAPv2 with StrongSwan.

[dstolfa]

StrongSwan on Void currently has issues with EAP-MSCHAPv2 in different ways.

(1) eap-identity needs to be enabled in order for config files with eap_identity=%any and similar lines to work (you essentially end up with EAP_NAK when EAP_IDENTITY is requested);
(2) eap-mschapv2 requires md4 to be enabled as a plugin
(3) eap-dynamic might be required on some setups, so this pull request enables it to avoid issues in the future.

General

• This is a new package and it conforms to the quality requirements

Have the results of the proposed changes been tested?

• I use the packages affected by the proposed changes on a regular basis and confirm this PR works for me
• I generally don't use the affected packages but briefly tested this PR

Does it build and run successfully?

(Please choose at least one native build and, if supported, at least one cross build. More are better.)

• I built this PR locally for my native architecture, (ARCH-LIBC)
• I built this PR locally for these architectures (if supported. mark crossbuilds):
  • aarch64-musl
  • armv7l
  • armv6l-musl

I have not tested if it runs on any of the cross builds, I simply tested that it indeed does build.