Bug 174143: Removed the obsolete platform.mk file. Do not allow overriding

of PLATFORM by the environment because PLATFORM is a common environment
variable.

security/coreconf/README

@@ -232,9 +232,6 @@ OVERVIEW of "config.mk":
         $(OS_CONFIG).mk         <architecture>-specific macros
                                 (dependent upon <architecture> tags)
 
-        platform.mk             source and release <platform> tags 
-				(dependent upon <architecture> tags)
-
         tree.mk                 release <tree> tags 
 				(dependent upon <architecture> tags)
 

security/coreconf/config.mk

@@ -70,9 +70,7 @@ endif
 # [4.0] Master "Core Components" source and release <platform> tags   #
 #       (dependent upon <architecture> tags)                          #
 #######################################################################
-ifndef PLATFORM
 PLATFORM = $(OBJDIR_NAME)
-endif
 
 #######################################################################
 # [5.0] Master "Core Components" release <tree> tags                  #