Forbid -Weverything

Use of -Weverything blocks build system changes and toolchain updates
on new warnings.  Forbid it in the build system.  Developers can
experiment with -Weverything on their module by adding it to their
Android.bp file and building with
m ANDROID_TEMPORARILY_ALLOW_WEVERYTHING=true

Fixes: 143713277
Test: manual
Change-Id: If154db328c52f687161e7a41e486d56a129850ac