tools: Check for abi-dumper in ./configure

This will be optional.  No functional change.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Ian Jackson <iwj@xenproject.org>
Release-Acked-by: Ian Jackson <iwj@xenproject.org>

config/Tools.mk.in

@@ -19,6 +19,7 @@ BCC                 := @BCC@
 IASL                := @IASL@
 AWK                 := @AWK@
 FETCHER             := @FETCHER@
+ABI_DUMPER          := @ABI_DUMPER@
 
 # Extra folder for libs/includes
 PREPEND_INCLUDES    := @PREPEND_INCLUDES@