sys.mk: Define HOST_CC as CC by default.

[stevek]

Summary

This allows for setting a different compiler for building hostprogs
when cross compiling.

Obtained from: Juniper Networks, Inc.

share/mk/sys.mk

 /* $FreeBSD$ */
 OUTPUT_FORMAT("elf64-x86-64-freebsd", "elf64-x86-64-freebsd", "elf64-x86-64-freebsd")
 OUTPUT_ARCH(i386:x86-64)
 ENTRY(btext)
 SEARCH_DIR("/usr/lib");
 SECTIONS
 {
   /* Read-only sections, merged into text segment: */
-  kernphys = CONSTANT (MAXPAGESIZE);
+  kernphys = 0x200000;
   . = kernbase + kernphys + SIZEOF_HEADERS;
   /*
    * Use the AT keyword in order to set the right LMA that contains
    * the physical address where the section should be loaded. This is
    * needed for the Xen loader which honours the LMA.
    */
   .interp         : AT (kernphys + SIZEOF_HEADERS) { *(.interp) }
   .hash           : { *(.hash) }