Debug + windows cbindgen install

Linux: print CC/HOSTCC/CFLAGS/MARCH/XC_HOST before make so next CI run reveals
why libwhich.o gets gcc invoked with x86_64 as a positional arg (failing with
'linker input file not found'). Local repro is missing so the only handle is
CI-side observability.

Windows: upstream dockcross/windows-shared-x64-posix has rustc+cargo but not
cbindgen — that comes from jgillis/dockcross 6a0fa8d, which is unpublished.
Install cbindgen ourselves to match the Linux variants.

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

Author: jgillis

Dockerfile.windows

@@ -24,8 +24,14 @@ ARG BASE_IMAGE=dockcross/windows-shared-x64-posix:latest
 
 FROM ${BASE_IMAGE}
 
-# Smoke test at image-build time. Confirms the dockcross base has the
-# polyglot pieces we expect (gcc cross to mingw, rustc, cargo, cbindgen).
+# Upstream dockcross/windows-shared-x64-posix has rustc+cargo but NOT
+# cbindgen (only jgillis/dockcross 6a0fa8d does — and that fork isn't
+# published as a public image). Install cbindgen ourselves to match the
+# Linux variants of this image.
+RUN cargo install cbindgen --version 0.28.0 \
+ && rm -rf "${CARGO_HOME:-/root/.cargo}/registry" "${CARGO_HOME:-/root/.cargo}/git" 2>/dev/null || true
+
+# Smoke test at image-build time. Confirms the polyglot pieces are in place.
 RUN ${CC} --version | head -1 && \
     ${CXX} --version | head -1 && \
     rustc --version && \

scripts/build-julia.sh

@@ -51,6 +51,21 @@ echo -n "glibc: "; ldd --version 2>&1 | head -1 || true
 set -o pipefail
 echo
 
+echo "=== Env vars Julia's Make.inc reads ==="
+for v in ARCH CC CXX FC HOSTCC HOSTCXX MARCH MCPU MTUNE CFLAGS CXXFLAGS \
+         CPPFLAGS LDFLAGS XC_HOST CROSS_TRIPLE CROSS_ROOT MAKEFLAGS MFLAGS; do
+  eval "val=\${$v-<unset>}"
+  printf '  %-15s = %s\n' "$v" "$val"
+done
+echo
+echo "=== Make's view (single-shot, no build) ==="
+# Print what Julia's outer make computes for the suspect vars without
+# actually building anything. Helps diagnose the libwhich x86_64 issue.
+make --no-print-directory print-CC print-HOSTCC print-CFLAGS \
+                          print-MARCH print-MCPU print-MTUNE 2>&1 \
+  | head -20 || true
+echo
+
 # Apply DISABLE_LIBUNWIND fix patches in-place via python string replacement.
 # This is more robust than `patch` against minor line-number drift across
 # Julia versions (the same fix submitted as JuliaLang/julia#61899). When the