10207 loader: libcrypto should use GNUC_ROOT

Reviewed by: Andy Fiddaman <andy@omniosce.org>
Reviewed by: Andrew Stormont <andyjstormont@gmail.com>
Reviewed by: Gergő Mihály Doma <domag02@gmail.com>
Approved by: Robert Mustacchi <rm@joyent.com>

usr/src/boot/sys/boot/libcrypto/Makefile.com

@@ -15,7 +15,7 @@
 
 include $(SRC)/Makefile.master
 
-CC=     $(GCC_ROOT)/bin/gcc
+CC=     $(GNUC_ROOT)/bin/gcc
 
 COMDIR = ../../../../../common/crypto