sysutils/grub2-efi: the port had been improved (+)
- Revert previous naive -fpermissive "fix" and #include <grub/env.h> to obtain the grub_env_set() prototype
- Replace RUN_DEPENDS manipulation with USE_GCC=yes:build and hand-rolled `do-install' target with INSTALL_WRKSRC
- While here, adjust LICENSE and wrap overly long lines
Fixes: 9bc25ee236c4
PR: 284483