devel/wasm3: Fix compilation and clean up port.

Rephrase COMMENT and pkg-descr to sound less like a sales pitch
Disable -march=native as this overrides settings by the framework and fails on multiple non x86 platforms
Remove GitHub related variables that are already defined
Replace += with = for GH_TUPLE
Remove forced O3 optimization

PR: 259701
Approved by: portmgr (build fix blanket)
Differential Revision: https://reviews.freebsd.org/D32883