BaseTools: Generate multiple rules when multiple output files

BaseTools: Generate multiple rules when multiple output files

This patch modifies the Makefile generation not to stop
adding Makfile rules when the first final target is found.
E.g.:
If the following rules are described in build_rule.txt:
 -[Rule1]: .X files generate .Y and .Z files;
 -[Rule2]: .Z files generate .Z1 files.
Currently, if a File1.X file was part of the sources of a
module, only [Rule1] would be generated in the Makefile.
Indeed, there are no rules to apply to .Y files: .Y files
are a final target. However, there is still [Rule2] to
apply to .Z files.

This patch also adds a dependency between the first
ouput file of a rule and the other output files.
For instance, with the same example as above, File1.Y
and File1.Z are generated by the following rule:
File1.Y: File1.X
    <Generate File1.Y>
    <Generate File1.Z>

and the new dependency is:
File1.Z: File1.Y

This is necessary to keep a dependency order during the
execution of the Makefile. Indeed, .Y and .Z files are
generated by the execution of a common set of commands,
and without this rule, there is no explicit dependency
relation between them.

Signed-off-by: Pierre Gondois <Pierre.Gondois@arm.com>
Suggested-by: Tomas Pilar <Tomas.Pilar@arm.com>
Reviewed-by: Bob Feng <bob.c.feng@intel.com>