Documentation/Make: add implementation/make_build_system.rst

This commit adds initial high level overview of the NuttX
make-based build system.  It documents:
* Tools used during the build process
* Mechanisms set in place during the build process

Signed-off-by: Luchian Mihai <luchiann.mihai@gmail.com>

Documentation/components/tools/index.rst

@@ -13,19 +13,6 @@ cmpconfig.c
 This C file can be used to build a utility for comparing two NuttX
 configuration files.
 
-Config.mk
----------
-
-Config.mk contains common definitions used by many configuration files.
-This file (along with <nuttx>/.config) must be included at the top of
-each configuration-specific Make.defs file like::
-
-    include $(TOPDIR)/.config
-    include $(TOPDIR)/tools/Config.mk
-
-Subsequent logic within the configuration-specific Make.defs file may then
-override these default definitions as necessary.
-
 checkpatch.sh
 -------------
 
@@ -740,6 +727,8 @@ these problems::
      -   option env="APPSDIR"
      +   default "../apps"
 
+.. _build_system_linking:
+
 link.sh, link.bat, copydir.sh, copydir.bat, unlink.sh, and unlink.bat
 ---------------------------------------------------------------------
 
@@ -780,6 +769,8 @@ this case.  link.bat will attempt to create a symbolic link using the
 NTFS mklink.exe command instead of copying files.  That logic, however,
 has not been verified as of this writing.
 
+.. _makefile_host:
+
 Makefile.host
 -------------
 
@@ -801,6 +792,8 @@ may be mounted under /etc in the NuttX pseudo file system.
 TIP: Edit the resulting header file and mark the generated data values
 as 'const' so that they will be stored in FLASH.
 
+.. _mkdeps:
+
 mkdeps.c, cnvwindeps.c, mkwindeps.sh, and mknulldeps.sh
 -------------------------------------------------------
 

Documentation/guides/versioning_and_task_names.rst

@@ -33,6 +33,8 @@ Answer
 
 This is probably normal behavior. There are two separate, unrelated issues here.
 
+.. _versioning:
+
 Versioning
 ----------
 

Documentation/implementation/index.rst

@@ -6,6 +6,7 @@ Implementation Details
    :maxdepth: 2
    :caption: Contents:
    
+   make_build_system.rst
    drivers_design.rst
    device_drivers.rst
    processes_vs_tasks.rst