moved PLATFORM and associated definitions from Makefile to kernel/Makefile so the kernel can be built by itself

git-svn-id: svn://anubis/hos/trunk@17 5b3e749e-e535-0410-8002-a9bb6afbdfca

Makefile

@@ -3,21 +3,6 @@ KERNEL_FILE := hos.gz
 MKISOFS     := genisoimage
 ISO         := hos.iso
 QEMU        := qemu-system-x86_64
-export PLATFORM := $(shell if [[ `uname` =~ "CYGWIN" ]]; then \
-                             echo cygwin; \
-                           else \
-                             echo unix; \
-                           fi)
-ifeq ($(PLATFORM), cygwin)
-export LD		:= i586-elf-ld
-export CC		:= i586-elf-gcc
-export CXX		:= i586-elf-g++
-else
-export LD      := ld
-export CC      := gcc
-export CXX     := g++
-endif
-export NASM    := nasm
 
 # default target: build the kernel and ISO image
 all: kernel iso
@@ -25,7 +10,7 @@ all: kernel iso
 # build the kernel
 .PHONY: kernel
 kernel:
-	make -C $@
+	$(MAKE) -C $@
 
 # build the ISO image
 .PHONY: iso
@@ -42,5 +27,5 @@ qemu: iso
 
 .PHONY: clean
 clean:
-	make -C kernel clean
+	$(MAKE) -C kernel clean
 	-rm -f $(ISO) iso/boot/$(KERNEL_FILE)