New port: graphics/shaderc, shader compiler for SPIR-V

[tobik]

Summary

Required for Vulkan support in multimedia/mpv.

Requires https://reviews.freebsd.org/D18711 and https://reviews.freebsd.org/D18712

[tobik]

graphics/shaderc/Makefile

24

Remove this. It's the default value for GH_PROJECT.

26–28

Why += ? In practice it is only ever needed for C*FLAGS, and LDFLAGS because they are already set in sys.mk (and possible make.conf by the user) which is included before everything else and we do not want to override those. This is not the case for CMAKE_{ON,OFF,ARGS} or basically any other variable unless you have set it before in the Makefile.

30

USES=localbase:ldflags

37

Use ECHO_CMD not ECHO (see Mk/bsd.commands.mk)

[tobik]

Apparently added as part of rP492060