BaseTools:Add [packages] section in dsc file

BZ:https://bugzilla.tianocore.org/show_bug.cgi?id=2270

Currently a PCD (e.g. FeaturePCD) cannot be used in a conditional
statement in a DSC/FDF file without a module in the build referencing
the PCD package DEC file.

An example implementation that to support this is to allow a [Packages]
section in the DSC file to list additional package dependencies for PCD
references in the package DSC/FDF files.

this patch is going to  add the ability to have the [packages] section
defined in the DSC file

Cc: Liming Gao <liming.gao@intel.com>
Cc: Bob Feng <bob.c.feng@intel.com>
Signed-off-by: Zhiju.Fan <zhijux.fan@intel.com>
Acked-by: Liming Gao <liming.gao@intel.com>
Reviewed-by: Bob Feng <bob.c.feng@intel.com>

BaseTools/Source/Python/Common/DataType.py

@@ -519,6 +519,7 @@ SECTIONS_HAVE_ITEM_AFTER_ARCH_SET = {TAB_LIBRARY_CLASSES.upper(), TAB_DEPEX.uppe
                                  PCDS_DYNAMICEX_VPD.upper(),
                                  PCDS_DYNAMICEX_HII.upper(),
                                  TAB_BUILD_OPTIONS.upper(),
+                                 TAB_PACKAGES.upper(),
                                  TAB_INCLUDES.upper()}
 
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