Specifies filenames or patterns matching one or more APKs that should be
uploaded to Google Play.
You can use wildcards like "**/build/outputs/*/*-release.apk".
See
the 'includes' attribute of Ant's FileSet for the exact format.
Note that multiple entries must be comma-separated.
The base directory is the build's workspace.
You can only upload APKs that are located in your workspace.
Applications which have several APKs per release, taking advantage of
Multiple APK Support, must have all of their APKs uploaded together, and
all APKs must have the same application identifier (APK package name).
This field supports substituting environment variables in the form
${SOME_VARIABLE} or $SOME_VARIABLE at build time.