Build libunwind before mingw-w64-libraries

When --unwindlib=libunwind is implicit, we need to build libunwind
to have a complete working C compiler too. Currently this is worked
around by initially creating a dummy, empty libunwind.a, but with
the current version of libcxx/libunwind, we can get rid of that
workaround if we build it as soon as possible.

Dockerfile

@@ -45,7 +45,7 @@ ARG TOOLCHAIN_ARCHS="i686 x86_64 armv7 aarch64"
 ARG DEFAULT_CRT=ucrt
 
 # Build everything that uses the llvm monorepo. We need to build the mingw runtime before the compiler-rt/libunwind/libcxxabi/libcxx runtimes.
-COPY build-llvm.sh build-lldb-mi.sh strip-llvm.sh install-wrappers.sh build-mingw-w64.sh build-mingw-w64-tools.sh build-compiler-rt.sh build-mingw-w64-libraries.sh build-libcxx.sh build-openmp.sh ./
+COPY build-llvm.sh build-lldb-mi.sh strip-llvm.sh install-wrappers.sh build-mingw-w64.sh build-mingw-w64-tools.sh build-compiler-rt.sh build-libcxx.sh build-mingw-w64-libraries.sh build-openmp.sh ./
 COPY wrappers/*.sh wrappers/*.c wrappers/*.h ./wrappers/
 RUN ./build-llvm.sh $TOOLCHAIN_PREFIX && \
     ./build-lldb-mi.sh $TOOLCHAIN_PREFIX && \
@@ -54,8 +54,8 @@ RUN ./build-llvm.sh $TOOLCHAIN_PREFIX && \
     ./build-mingw-w64.sh $TOOLCHAIN_PREFIX --with-default-msvcrt=$DEFAULT_CRT && \
     ./build-mingw-w64-tools.sh $TOOLCHAIN_PREFIX && \
     ./build-compiler-rt.sh $TOOLCHAIN_PREFIX && \
-    ./build-mingw-w64-libraries.sh $TOOLCHAIN_PREFIX && \
     ./build-libcxx.sh $TOOLCHAIN_PREFIX && \
+    ./build-mingw-w64-libraries.sh $TOOLCHAIN_PREFIX && \
     ./build-compiler-rt.sh $TOOLCHAIN_PREFIX --build-sanitizers && \
     ./build-openmp.sh $TOOLCHAIN_PREFIX && \
     rm -rf /build/*