From SDK Tools : ( SDK Tools, Revision 8 (December 2010) )
Support for a true debug build.
Developers no longer need to add the
android:debuggable
attribute to the
<application>
tag in the manifest —
the build tools add the attribute automatically. In Eclipse/ADT, all
incremental builds are assumed to be
debug builds, so the tools insert
android:debuggable="true"
. When
exporting a signed release build,
the tools do not add the attribute.
In Ant, aant debug
command
automatically inserts the
android:debuggable=”true” attribute,
whileant release
does not. If android:debuggable=”true” is manually
set, thenant release
will actually do
a debug build, rather than a release
build.