Android LTO caused a 70-90% build time regression (WONTFIX'd bug 1483990). Developers want fast local builds and try runs, so we should disable LTO in non-shipping builds (i.e. non-PGO opt and debug).
Once we have Android PGO builds (bug 632954), we can disable LTO for opt builds. PGO would then imply LTO, like clang-cl did on Windows in bug 1475660.
Would we want to disable LTO for opt builds in all branches (autoland, inbound, central, and try) or just on autoland, inbound, and try? Is there value in building and testing opt with LTO in central in addition to opt without LTO on autoland and inbound? Any bugs we find in one of those configurations but not the other is most likely a compiler bug, not a Firefox bug. Do we care?