Address some confusing points

- stage N+1 -> stage N artifacts
- Use more likely examples of an ABI break
- stage N -> stage N compiler

Author: jyn514

src/building/bootstrapping.md

@@ -144,17 +144,17 @@ built by `build --stage N compiler/rustc` -- that's 'stage N artifacts'
 ('the compiler built by stage N').
 
 In short, _stage 0 uses the stage0 compiler to create stage0 artifacts which
-will later be uplifted to stage1_.
+will later be uplifted to be the stage1 compiler_.
 
 In each stage, two major steps are performed:
 
 1. `std` is compiled by the stage N compiler.
 2. That `std` is linked to programs built by the stage N compiler, including
-   the stage (N+1) compiler.
+   the stage N artifacts (stage (N+1) compiler).
 
-This is somewhat intuitive if one thinks of the stage (N+1) compiler as "just"
+This is somewhat intuitive if one thinks of the stage N artifacts as "just"
 another program we are building with the stage N compiler:
-`build --stage N compiler/rustc` is linking the stage (N+1) compiler to the `std`
+`build --stage N compiler/rustc` is linking the stage N artifacts to the `std`
 built by the stage N compiler.
 
 Here is a chart of a full build using `x.py`:
@@ -174,11 +174,12 @@ Note that there are two `std` libraries in play here:
 2. The library _used to compile programs_ with `stageN/rustc`, which was
    built by stage N (stage N `std`).
 
-stage N `std` is pretty much necessary for any useful work with the compiler.
+stage N `std` is pretty much necessary for any useful work with the stage N compiler.
 Without it, you can only compile programs with `#![no_core]` -- not terribly useful!
 
 The reason these need to be different is because they aren't necessarily ABI-compatible:
-there could be a new layout optimization on nightly that isn't present in `beta`.
+there could be a new layout optimizations, changes to MIR, or other changes
+to Rust metadata on nightly that aren't present in `beta`.
 
 This is also where `--keep-stage 1 library/std` comes into play. Since most
 changes to the compiler don't actually change the ABI, once you've produced a