[Android] Stop doing manual argument separation in javac.py.

Stop doing nonsensical things like calling str.split() to manually split
option arguments since it obviously breaks arguments with spaces.

Instead, make "--src-dirs", "--javac-includes" and "--classpath"
accumulate its arguments, and just pass them multiple times in
make_apk.py.

BUG=XWALK-1905

(cherry picked from commit 2fd3337df93ee8300533ba7a9559af427546e403)

Conflicts:
	app/tools/android/make_apk.py
Merge pull request #2084 from rakuco/xwalk6-javac-call-backport

[Android] Stop doing manual argument separation in javac.py.