Build at /work to match local successful build path

User's local Julia cross-build that produced julia.exe ran at
/work/julia-1.12.6/. My polyglot Dockerfile used /build/julia-1.12.6/.
Both LLVM CMake and Julia's deps Makefiles cache absolute paths in
CMakeCache.txt; on a path-sensitive lookup the difference between /work
and /build could explain why CI hits the vt_gen failure (NATIVE sub-build
doesn't produce NATIVE/bin/llvm-min-tblgen) while local doesn't.

Cheap experiment: match the proven-good WORKDIR.

Signed-off-by: Joris Gillis <joris@yacoda.com>

Author: jgillis

Dockerfile

@@ -212,7 +212,12 @@ FROM toolchain AS julia-builder
 ARG JULIA_VERSION=1.12.6
 ARG BUILD_JOBS=1
 
-WORKDIR /build
+# Build under /work (not /build) to match the WORKDIR of the original
+# successful local build at ~/work/julia-build/. CMake caches absolute
+# paths in CMakeCache.txt; if Julia's deps/llvm.mk or the sub-make have
+# any path-sensitive lookup, matching the proven-good path is the cheap
+# safe choice.
+WORKDIR /work
 RUN curl -fsSL -o "julia-${JULIA_VERSION}-full.tar.gz" \
       "https://github.com/JuliaLang/julia/releases/download/v${JULIA_VERSION}/julia-${JULIA_VERSION}-full.tar.gz" \
  && tar xzf "julia-${JULIA_VERSION}-full.tar.gz" \
@@ -248,7 +253,7 @@ MMTK_PLAN := None
 JULIA_CPU_TARGET := generic;sandybridge,-xsaveopt,clone_all;haswell,-rdrnd,base(1);x86-64-v4,-rdrnd,base(1)
 EOF
 
-WORKDIR /build/julia-${JULIA_VERSION}
+WORKDIR /work/julia-${JULIA_VERSION}
 # BUILD_JOBS=1 to avoid the BuildKit `docker build` parallel-make race
 # (stray $(ARCH) token leaks into a gcc invocation in dep configures).
 # Cross-build is slow regardless — LLVM dominates.
@@ -268,7 +273,7 @@ FROM toolchain
 ARG JULIA_VERSION=1.12.6
 
 # Carry the cross-built Julia install (usr/ is the install prefix).
-COPY --from=julia-builder /build/julia-${JULIA_VERSION}/usr /opt/julia
+COPY --from=julia-builder /work/julia-${JULIA_VERSION}/usr /opt/julia
 ENV JULIA_HOME=/opt/julia \
     JULIA_PATH=/opt/julia \
     JULIA_VERSION=${JULIA_VERSION}