x86, boot: Document intermediates more clearly

This adds a comment detailing the various intermediate files used to build
the bootable decompression image for the x86 kernel.

Signed-off-by: Kees Cook <[e-mail]>
Reviewed-by: Josh Triplett <[e-mail]>
Cc: Matt Fleming <[e-mail]>
Cc: Ard Biesheuvel <[e-mail]>
Cc: Junjie Mao <[e-mail]>
Link: http://lkml.kernel.org/r/[e-mail]
Signed-off-by: Thomas Gleixner <[e-mail]>

arch/x86/boot/compressed/Makefile

···
 #
 # create a compressed vmlinux image from the original vmlinux
 #
+# vmlinuz is:
+#	decompression code (*.o)
+#	asm globals (piggy.S), including:
+#		vmlinux.bin.(gz|bz2|lzma|...)
+#
+# vmlinux.bin is:
+#	vmlinux stripped of debugging and comments
+# vmlinux.bin.all is:
+#	vmlinux.bin + vmlinux.relocs
+# vmlinux.bin.(gz|bz2|lzma|...) is:
+#	(see scripts/Makefile.lib size_append)
+#	compressed vmlinux.bin.all + u32 size of vmlinux.bin.all
 
 targets := vmlinux vmlinux.bin vmlinux.bin.gz vmlinux.bin.bz2 vmlinux.bin.lzma \
 	vmlinux.bin.xz vmlinux.bin.lzo vmlinux.bin.lz4