fixes

builder/docker/Dockerfile

@@ -5,7 +5,7 @@ FROM ubuntu:24.04 AS sysroot
 ARG FREEBSD_RELEASE=15.1-RELEASE
 ARG FREEBSD_MIRROR=https://download.freebsd.org/releases/amd64/amd64
 RUN apt-get update && DEBIAN_FRONTEND=noninteractive apt-get install -y --no-install-recommends \
-        ca-certificates wget xz-utils \
+    ca-certificates wget xz-utils \
     && rm -rf /var/lib/apt/lists/*
 WORKDIR /tmp/freebsd
 RUN set -eux; \
@@ -21,11 +21,16 @@ RUN set -eux; \
 # RustProxy requires rust-version = 1.88.
 FROM rust:1.88-slim-bookworm AS builder
 RUN apt-get update && DEBIAN_FRONTEND=noninteractive apt-get install -y --no-install-recommends \
-        ca-certificates clang lld llvm file git perl pkg-config python3 \
+    ca-certificates clang lld llvm file git perl pkg-config python3 \
     && rm -rf /var/lib/apt/lists/*
 
 COPY --from=sysroot /freebsd-sysroot /opt/freebsd-sysroot
-RUN rustup target add x86_64-unknown-freebsd
+
+ENV RUSTUP_TOOLCHAIN=1.88.0
+
+RUN rustup target add \
+    --toolchain 1.88.0 \
+    x86_64-unknown-freebsd
 
 ENV CARGO_TARGET_X86_64_UNKNOWN_FREEBSD_LINKER=clang \
     CC_x86_64_unknown_freebsd=clang \