BaseTools:fix regression issue for platform .map file

BaseTools:fix regression issue for platform .map file

BZ:https://bugzilla.tianocore.org/show_bug.cgi?id=2363

This patch is to fix a build tool regression issue which was introduced
by commit b8ac0b7f28.This issue caused map file lost the line of IMAGE=***.
For example,in Ovmf.map, there is no line of (IMAGE=<path to efi> ) under
each of modules item.

The path to the efi file generated by each module is written on this line
The purpose of this line is add the debug image full path.
there is no information about the module in the map file other than FVName,
it allows us to quickly know which module this part corresponds to.

In commit b8ac0b7f28,add a line ("self.BuildModules = []") in function,
but it's used to calculate the variable ModuleList in the following code.

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