ci: install Go in CI builder for aws-lc-fips-sys

[jasonhernandez]

Summary

Install Go 1.24.2 in the CI builder image (ci/builder/Dockerfile). Required by aws-lc-fips-sys, which builds BoringSSL's FIPS module from source and needs Go for integrity verification.

This is needed because cargo-test runs with --all-features, which enables the mz-ore fips feature → aws-lc-rs/fips → aws-lc-fips-sys → cmake → requires Go.

Without this, rust-cargo-test-2 fails with:

CMake Error at aws-lc/cmake/go.cmake:6 (message):
  Could not find Go

Change

# +4 lines in ci/builder/Dockerfile
RUN curl -fsSL https://go.dev/dl/go1.24.2.linux-$ARCH_GO.tar.gz | tar -C /usr/local -xzf -
ENV PATH="/usr/local/go/bin:${PATH}"

Fixes SEC-232.

Test plan

• CI builder image builds successfully
• rust-cargo-test-2 passes with --all-features (no more "Could not find Go")

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[jasonhernandez]

Folded into PR #35843 (part of the FIPS PR chain where the fips feature is introduced).