Rollup merge of #120167 - dtolnay:bootstrap, r=clubby789

Capture the rationale for `-Zallow-features=` in bootstrap.py

Based on the discussion in https://github.com/rust-lang/rust/pull/120096.
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Matthias Krüger 2024-01-21 12:28:54 +01:00 committed by GitHub
commit ac713695f3
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@ -924,17 +924,29 @@ class RustBuild(object):
# default toolchain is not nightly.
#
# But that setting has the collateral effect of rust-analyzer also
# passing RUSTC_BOOTSTRAP=1 to all x.py invocations too (the various overrideCommand).
# For compiling bootstrap that can cause spurious rebuilding of bootstrap when
# rust-analyzer x.py invocations are interleaved with handwritten ones on the
# command line.
# passing RUSTC_BOOTSTRAP=1 to all x.py invocations too (the various
# overrideCommand).
#
# Set RUSTC_BOOTSTRAP=1 consistently.
# Set a consistent RUSTC_BOOTSTRAP=1 here to prevent spurious rebuilds
# of bootstrap when rust-analyzer x.py invocations are interleaved with
# handwritten ones on the command line.
env["RUSTC_BOOTSTRAP"] = "1"
default_rustflags = "" if env.get("RUSTFLAGS_BOOTSTRAP", "") else "-Zallow-features="
env.setdefault("RUSTFLAGS", default_rustflags)
# If any of RUSTFLAGS or RUSTFLAGS_BOOTSTRAP are present and nonempty,
# we allow arbitrary compiler flags in there, including unstable ones
# such as `-Zthreads=8`.
#
# But if there aren't custom flags being passed to bootstrap, then we
# cancel the RUSTC_BOOTSTRAP=1 from above by passing `-Zallow-features=`
# to ensure unstable language or library features do not accidentally
# get introduced into bootstrap over time. Distros rely on being able to
# compile bootstrap with a variety of their toolchains, not necessarily
# the same as Rust's CI uses.
if env.get("RUSTFLAGS", "") or env.get("RUSTFLAGS_BOOTSTRAP", ""):
# Preserve existing RUSTFLAGS.
env.setdefault("RUSTFLAGS", "")
else:
env["RUSTFLAGS"] = "-Zallow-features="
target_features = []
if self.get_toml("crt-static", build_section) == "true":