Revert "CI: build FreeBSD artifacts on FreeBSD 13.4"

This reverts commit cf34545.

That commit led to a regression of
#132185 .  So my analysis that
the problem lay in FreeBSD 13.2's specific LLVM version was clearly
wrong.  Revert that commit until we can figure out the real root cause.

Fixes #132185

Author: asomers

src/ci/docker/host-x86_64/dist-x86_64-freebsd/Dockerfile

@@ -29,9 +29,9 @@ COPY scripts/cmake.sh /scripts/
 RUN /scripts/cmake.sh
 
 ENV \
-    AR_x86_64_unknown_freebsd=x86_64-unknown-freebsd13-ar \
-    CC_x86_64_unknown_freebsd=x86_64-unknown-freebsd13-clang \
-    CXX_x86_64_unknown_freebsd=x86_64-unknown-freebsd13-clang++
+    AR_x86_64_unknown_freebsd=x86_64-unknown-freebsd12-ar \
+    CC_x86_64_unknown_freebsd=x86_64-unknown-freebsd12-clang \
+    CXX_x86_64_unknown_freebsd=x86_64-unknown-freebsd12-clang++
 
 ENV HOSTS=x86_64-unknown-freebsd
 

src/ci/docker/scripts/freebsd-toolchain.sh

@@ -5,8 +5,8 @@ set -eux
 
 arch=$1
 binutils_version=2.40
-freebsd_version=13.4
-triple=$arch-unknown-freebsd13
+freebsd_version=12.3
+triple=$arch-unknown-freebsd12
 sysroot=/usr/local/$triple
 
 hide_output() {
@@ -59,7 +59,7 @@ done
 
 # Originally downloaded from:
 # URL=https://download.freebsd.org/ftp/releases/${freebsd_arch}/${freebsd_version}-RELEASE/base.txz
-URL=https://ci-mirrors.rust-lang.org/rustc/2024-09-13-freebsd-${freebsd_version}-${freebsd_arch}-base.txz
+URL=https://ci-mirrors.rust-lang.org/rustc/2022-05-06-freebsd-${freebsd_version}-${freebsd_arch}-base.txz
 curl "$URL" | tar xJf - -C "$sysroot" --wildcards "${files_to_extract[@]}"
 
 # Clang can do cross-builds out of the box, if we give it the right