This patch contains a number of changes to the gyp_reader code:
* Add three new flags to GYP_DIRS:
** no_chromium, to skip forcing the includes/etc needed for chromium gyp files
** no_unified, to force building all sources without unification
** action_overrides, to pass scripts used when mapping gyp actions to moz.build GENERATED_FILES
* Handle the flags mentioned above in read_from_gyp
* Handle actions in gyp targets by mapping them to GENERATED_FILES, using scripts specified in the action_overrides flag. We don't try to handle the generic action case, we require special-casing for each action.
* Handle a subset of copies in gyp targets by mapping them to EXPORTS, just enough to handle the use of them for NSS exports.
* Handle shared_library and executable gyp targets
* Handle gyp target dependencies/libraries as USE_LIBS/OS_LIBS
* Handle generated source files
* Handle .def files in sources by mapping them to SYMBOLS_FILE
* Special-case some include_dirs:
** Map `<(PRODUCT_DIR)/dist/` to $DIST/include (to handle include paths for NSS exports)
** Map include_dirs starting with topobjdir to objdir-relative paths, to handle passing the NSPR include path to NSS
* split /build/gyp.mozbuild into two parts, with gyp_base.mozbuild containing generic bits, and gyp.mozbuild containing chromium-specific bits


MozReview-Commit-ID: FbDmlqDjRp4

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extra : rebase_source : d3fb470c589f92d8c956b9ecd550fb8df79ff5bc