GN: Refactor webrtc/base/BUILD.gn
GN: Refactor webrtc/base/BUILD.gn

Move the all_dependent_configs configurations into
a single config for better readability.

Sync the Mac and iOS frameworks between the GYP and the GN
build. Many entries that used to be default included in
https://code.google.com/p/chromium/codesearch#chromium/src/build/config/BUILD.gn
are no longer implicitly added for Mac, so to ensure they are
they're added back for the Mac build.

NOTRY=True

Review URL: https://codereview.webrtc.org/1914913002

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#12484}

TimothyGu/libilbc,ShiftMediaProject/libilbc,ShiftMediaProject/libilbc,ShiftMediaProject/libilbc,TimothyGu/libilbc,ShiftMediaProject/libilbc,ShiftMediaProject/libilbc,TimothyGu/libilbc,TimothyGu/libilbc,TimothyGu/libilbc