Added usage and notes

git-svn-id: https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2@2734 6f19259b-4bc3-4df7-8a09-765794883524

BaseTools/ReadMe.txt

@@ -11,4 +11,26 @@ Current state of the tools is Proto-Type - not all tool functions have been impl
 and there may be bugs in these tools.  These tools are under constant development at
 this time.
 
-20-Jun-2007
+BaseTools Simple Usage:
+1) Change the directory to the EDK2 root directory, where the edksetup.bat is
+2) Run "edksetup.bat NewBuild"
+3) Set the ACTIVE_PLATFORM to your desired platform description file 
+   (%WORKSPACE%\Conf\target.txt)
+4) To build platform, run "build" command in non-module directory
+5) To build module individually, run "build" command in module directory, i.e. where the 
+   *.inf file is
+
+Notes:
+1) Only *.efi files can be generated. Flash image cannot be generated at present.
+2) Only "clean" and "cleanall" build target are supported, in both top level 
+   makefile and module's makefile. 
+3) Not all tool chains and target architectures are tested. Due to both tools 
+   and source code limitations, ther must be bugs in it. Please report any issue 
+	 ASAP so we can fix it soon.
+4) The tree structure generated by build tools is similar to Ant build system.
+5) Makefile can be called directly by nmake for both top level platform and module. But
+   after you call "nmake cleanall", you have to call "build" command to rebuild platform
+	 or modules because the AutoGen.* files have been be removed. The "makefile" itself
+	 cannot generate AutoGen.* files. Only "build" command can.
+
+25-Jun-2007