Use bsd.compiler.mk instead of src.opts.mk

• MK_PROFILE is controlled in bsd.opts.mk, which is pulled in via bsd.own.mk, which is pulled in via bsd.init.mk . All upstream Makefiles which build off of this one use bsd.init.mk.
• COMPILER_{TYPE,VERSION} is set via bsd.compiler.mk .

This reduces the namespace pollution/complexity somewhat.

MFC after: 1 week