scons: add helpers to access GDB XML description files

Change-Id: Ic3b18887544b7710ed07a86d28dc62d8441b3476
Reviewed-on: https://gem5-review.googlesource.com/c/15255
Reviewed-by: Gabe Black <gabeblack@google.com>
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Maintainer: Gabe Black <gabeblack@google.com>

src/SConscript

@@ -293,6 +293,9 @@ def Blob(blob_path, symbol):
                 MakeAction(embedBlob, Transform("EMBED BLOB")))
     Source(cpp_path)
 
+def GdbXml(xml_id, symbol):
+    Blob(joinpath(gdb_xml_dir, xml_id), symbol)
+
 class Source(SourceFile):
     ungrouped_tag = 'No link group'
     source_groups = set()
@@ -522,6 +525,7 @@ class Gem5(Executable):
 
 # Children should have access
 Export('Blob')
+Export('GdbXml')
 Export('Source')
 Export('PySource')
 Export('SimObject')