android: Don't emit useless info into generated makefiles.

android: Don't emit useless info into generated makefiles.

To make the generated makefiles smaller and slightly easier to debug,
omit information that is useless:

* Don't emit LDFLAGS for static libraries as the linker is not invoked.

* For static libraries, only include system libraries in the lists of
  libraries to link against. The system libraries are required in case
  they provide implicit include paths, but there's no need to include
  the large list of gyp-generated targets.

* Don't emit empty lists of libraries to link against.

* Don't bother setting LOCAL_MODULE_TAGS to optional as that's the
  default value.

Also, stop attempting to remove standard system include paths; the list
is out of date, never matches anything in the Chromium build, and it
doesn't really matter if a standard path is duplicated anyway.

BUG=
R=primiano@chromium.org

Committed: https://code.google.com/p/gyp/source/detail?r=1976

[Torne, 2014-09-12 12:59:13]

torne@chromium.org changed reviewers:
+ primiano@chromium.org

[Torne, 2014-09-12 12:59:14]

This passes all the gyp-android tests locally and I can still build
libwebviewchromium with this change.

[Primiano Tucci (use gerrit), 2014-09-12 14:02:23]

lgtm

[Torne, 2014-09-12 14:59:35]

Committed patchset #1 (id:1) manually as 1976 (presubmit successful).