build: Drop docs about old build engine

No longer valid.
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>

Documentation/Makefile.build.txt

-Makefile.build(1)
-=================
-:doctype:       manpage
-:man source:    CRtools
-:man version:   0.0.2
-:man manual:    CRtools Manual
-
-NAME
-----
-Makefile.build - a bunch of helpers for simplified Makefiles
-
-
-SYNOPSIS
---------
-'make' -f scripts/Makefile.build obj=<dir>
-
-
-DESCRIPTION
------------
-
-This is main build helpers script we use. Basically the idea is to minimize hand
-work and describe Makefiles with somewhat simplified grammar.
-
-The script may work in two modes
-
-	- *Default mode*
-
-	- *Target mode*
-
-Following keywords are reserved and must not be used for anything else --
-'targets', 'deps', 'all-obj', 'incdeps', 'obj-y', 'obj-e', 'asm-y', 'asm-e',
-'file', 'libs-e', '<x>-obj-y', '<x>-obj-e', '<x>-asm-y', '<x>-asm-e',
-'<x>-obj-y-cflags', '<x>-obj-e-cflags', '<x>-asm-y-asmflags', '<x>-asm-e-asmflags',
-'<x>-libs-e'. Where '<x>' is a prefix of the target, will be explained below.
-That said, do not use such names for other purposes as stated here.
-
-OBJ=
-----
-
-Parameter *obj=* states for passing directory where simplified Makefile lays in.
-Note the directory name must not end up with a slash, it is mandatory.
-
-In your simplifiled Makefile you still can refer to it as '$(obj)' variable. If
-you need an ending slash, just type it explicitly as '$(obj)/'.
-
-DEFAULT MODE
-------------
-
-In *default* mode the script builds '$(obj)/built-in.o' relocatable file. To use
-*default* mode do not ever mention '<x>-' and 'targets' variables in a Makefile.
-This done for simplicity, otherwise more complex logic will be needed in the
-script which slows down built procedure.
-
-Thus in *default* mode the following variables may and should be referred
-
-obj-y::
-	Source code C file. Typically refered as *obj-y += 'some-file.o'*.
-	This implies you have real 'some-file.c' in '$(obj)' directory.
-
-obj-x::
-	Same as 'obj-y' but the output files have the suffix $(xsuffix).
-	This is used when building shared source file for both pie and crtools
-	The posfix '-x' came from word 'extra'.
-
-obj-e::
-	Same as 'obj-y' but implies that source code file lays in directory
-	other than '$(obj)'. The postfix '-e' came from word 'external'.
-
-obj-ext-src-y::
-	Same as 'obj-y' but implies that source code file lays in directory
-	other than '$(obj)', while compiled object file pushed into '$(obj)' directory.
-	Consider using this variable if you need to compile same source file with
-	different flags.
-
-asm-y::
-	Source code S file. Same as 'obj-y' but for assembly language.
-
-asm-e::
-	Same as 'obj-e' but for assembly language.
-
-lib-e::
-	Some extarnal library the 'built-in.o' should link with.
-
-lib-so::
-	Tells the make engine to build a shared library.
-
-incdeps::
-	A flag which tells the script to generate dependency (that named '*.d'
-	files)	for source code C files. To turn this functionality on just
-	type 'incdeps := y' somewhere in your Makefile.
-
-cleanup-y::
-	List of files to be cleaned up when 'clean' target is called.
-
-For example a simplified Makefile may look like
-
-	obj-y += file1.o
-	obj-y += file2.o
-	obj-y += file3.o
-
-	ifneq ($(MAKECMDGOALS),clean)
-	incdeps := y
-	endif
-
-TARGET MODE
------------
-
-In *target* mode the script builds all targets declared in a Makefile. Thus the
-final built relocatable files will have a name as '<x>.built-in.o', where '<x>'
-is a name of a target (I will continue using '<x>' to refer the target name).
-The following variables may be used for *target* mode.
-
-targets::
-	This one defines a target name to built.
-
-<x>-obj-y::
-	Same as 'obj-y' but per target.
-
-<x>-obj-y-cflags::
-	Additional compiler flags for this target and object files
-	in '<x>-obj-y'.
-
-<x>-obj-e::
-	Same as 'obj-e' but per target.
-
-<x>-obj-e-cflags::
-	Additional compiler flags for this target and object files
-	in '<x>-obj-e'.
-
-<x>-asm-y::
-	Same as 'asm-y' but per target.
-
-<x>-asm-y-asmflags::
-	Additional compiler flags for this target and object files
-	in '<x>-asm-y'.
-
-<x>-asm-e::
-	Same as 'asm-e' but per target.
-
-<x>-asm-e-asmflags::
-	Additional compiler flags for this target and object files
-	in '<x>-asm-e'.
-
-<x>-libs-e::
-	Same as 'libs-e' but per-target.
-
-There might be a situation where we have several targets and each of them need
-some object file to be linked in. In this case we need to use variables from
-*default* mode. Better to explain with example.
-
-Lets say we need to built two targets 'one' and 'two' (thus 'one.built-in.o' and
-'two.built-in.o' relocatable files will be generated). For 'one' we need to use
-files 'a.o', 'b.o', and for 'two' we need to use 'c.o' and 'd.o'. But both
-targets need functionality from file 'e.o'. To force the script share the 'e.o'
-we describe it as plain 'obj-y'.
-
-	targets += one
-	targets += two
-
-	one-obj-y += a.o
-	one-obj-y += b.o
-
-	two-obj-y += c.o
-	two-obj-y += d.o
-
-	obj-y += e.o
-
-The script will compile all files and link 'one.built-in.o' from files 'one-obj-y'
-plus 'obj-y'. The same applies to the target 'two' ('obj-y' file will be linked
-in as well).
-
-Thus if you refer variables from *default* mode but have 'targets' defined, the
-script will treat such variables as a sign to share the productions at moment
-when targets get linked.
-
-INVISIBLE RULES
----------------
-
-If the script is used for build procedure then a couple of additional rules are
-generated on the fly. Better to explain with example again.
-
-Lets say we have a Makefile with the following contents
-
-	obj-y += file.o
-
-where $(obj) is a directory named 'dir'. So once we use the script we can
-generate the following files.
-
-make dir/file.o::
-	To compile the file.
-
-make dir/file.s::
-	To generate assembly file from C file.
-
-make dir/file.d::
-	To generate dependency file.
-
-make dir/file.i::
-	To generate C file with preprocessor only.