updates after feedback from discussions

Author: davidtwco

src/2025h1/build-std.md

@@ -27,7 +27,8 @@ library, this is useful for a variety of reasons:
 - Re-building the standard library with different configuration options (e.g. changing the
   optimisation level, using flags which change the ABI, or which add additional exploit
   mitigations).
-- Re-building the standard library with different `cfg`s (e.g. disabling `backtrace` in std).
+- Re-building the standard library with different `cfg`s (e.g. disabling `backtrace` in std), to
+  the extent that such configurations are supported by the standard library.
 - Stabilisation of various compiler flags which change the ABI, add additional exploit
   mitigations (such as `-Zsanitizers=cfi` or `-Zbranch-protection`), or which otherwise only make
   sense to use when the entire program is compiled with the flag (including std) is blocked on
@@ -37,6 +38,20 @@ These features are more useful for some subsets of the Rust community, such as e
 where optimising for size can be more important and where the targets often don't ship with a
 pre-compiled std.
 
+The fifty-thousand foot view of the work involved in this feature is:
+
+- Having the standard library sources readily available that match the compiler.
+- Being able to build those sources without using a nightly toolchain, which has many
+  possible solutions.
+- Having a blessed way to build at least `core` without Cargo, which some users like
+  Rust for Linux would like.
+  - This would be optional but may be a side-effect of whatever mechanism for build-std
+    the MVP RFC eventually proposes.
+- Being able to tell the compiler to use the resulting prebuilt standard library sources
+  instead of the built-in standard library, in a standard way.
+- Integrating all of the above into Cargo.
+- Making sure all of this works for targets that don't have a pre-built std.
+
 Rust for Linux and some other projects have a requirement to build core themselves without Cargo
 (ideally using the same stable compiler they use for the rest of their project), which is a shared
 requirement with build-std, as whatever mechanism these projects end up using could be re-used by
@@ -50,6 +65,14 @@ since its initial development in 2019/2020. There are a variety of issues in the
 experimental implementation to vague "investigate and think about this" issues, which make the
 feature difficult to make progress on. 
 
+Some of the work required for this exists in the current perma-unstable `-Zbuild-std`
+implementation, which may be re-used if appropriate.
+
+Prior to the submission of this goal, this goal has been discussed with the cargo team and
+leads of the compiler and library teams, ensuring that this goal's owners have liaisons from
+stakeholder teams and the support of the primary teams involved in the design and
+implementation.
+
 [wg-cargo-std-aware]: https://github.com/rust-lang/wg-cargo-std-aware
 
 ### The next 6 months
@@ -99,9 +122,6 @@ which can be designed and implemented to complete the build-std feature.
 | ↳ Author RFC                                   | @adamgemmell         |       |
 | ↳ Implementation                               | @adamgemmell         |       |
 | ↳ Standard reviews                             | ![Team][] [cargo]    |       |
-| ↳ RFC decision                                 | ![Team][] [cargo]    |       |
-| ↳ Author stabilization report                  | @adamgemmell         |       |
-| ↳ Stabilization decision                       | ![Team][] [cargo]    |       |
 
 ### Definitions