ci: Add MSVC builds

This adds MSVC builds built on Linux using wine. This requires some
settings of tools and flags because the autotools support for MSVC is
naturally somewhat limited.

The advantage of this approach is that it is compatible with our
existing CI scripts, so there's no need to write a Windows CI script
(in PowerShell or similar). If we want to test building and running on
Windows native (e.g., as supported by Cirrus CI) we could still do this
in the future.

Another advantage of this approach is that contributors can simply use
the docker image if they need a MSVC installation in a non-Windows
environment.

This commit also improves the Dockerfile by grouping RUN commands
according to Docker docs:
https://docs.docker.com/develop/develop-images/dockerfile_best-practices/#run

.cirrus.yml

@@ -263,6 +263,42 @@ task:
     - ./ci/cirrus.sh
   << : *CAT_LOGS
 
+task:
+  << : *LINUX_CONTAINER
+  env:
+    WRAPPER_CMD: wine
+    WERROR_CFLAGS: -WX
+    WITH_VALGRIND: no
+    ECDH: yes
+    RECOVERY: yes
+    EXPERIMENTAL: yes
+    SCHNORRSIG: yes
+    CTIMETEST: no
+    # Set non-essential options that affect the CLI messages here.
+    # (They depend on the user's taste, so we don't want to set them automatically in configure.ac.)
+    CFLAGS: -nologo -diagnostics:caret
+    LDFLAGS: -XCClinker -nologo -XCClinker -diagnostics:caret
+  # Use a MinGW-w64 host to tell ./configure we're building for Windows.
+  # This will detect some MinGW-w64 tools but then make will need only
+  # the MSVC tools CC, AR and NM as specified below.
+  matrix:
+    - name: "x86_64 (MSVC): Windows (Debian stable, Wine)"
+      env:
+        HOST: x86_64-w64-mingw32
+        CC: /opt/msvc/bin/x64/cl
+        AR: /opt/msvc/bin/x64/lib
+        NM: /opt/msvc/bin/x64/dumpbin -symbols -headers
+    - name: "i686 (MSVC): Windows (Debian stable, Wine)"
+      env:
+        HOST: i686-w64-mingw32
+        CC: /opt/msvc/bin/x86/cl
+        AR: /opt/msvc/bin/x86/lib
+        NM: /opt/msvc/bin/x86/dumpbin -symbols -headers
+  << : *MERGE_BASE
+  test_script:
+    - ./ci/cirrus.sh
+  << : *CAT_LOGS
+
 # Sanitizers
 task:
   << : *LINUX_CONTAINER

ci/cirrus.sh

@@ -9,6 +9,7 @@ env >> test_env.log
 
 $CC -v || true
 valgrind --version || true
+$WRAPPER_CMD --version || true
 
 ./autogen.sh
 

ci/linux-debian.Dockerfile

@@ -1,15 +1,14 @@
 FROM debian:stable
 
-RUN dpkg --add-architecture i386
-RUN dpkg --add-architecture s390x
-RUN dpkg --add-architecture armhf
-RUN dpkg --add-architecture arm64
-RUN dpkg --add-architecture ppc64el
-RUN apt-get update
+RUN dpkg --add-architecture i386 && \
+    dpkg --add-architecture s390x && \
+    dpkg --add-architecture armhf && \
+    dpkg --add-architecture arm64 && \
+    dpkg --add-architecture ppc64el
 
 # dkpg-dev: to make pkg-config work in cross-builds
 # llvm: for llvm-symbolizer, which is used by clang's UBSan for symbolized stack traces
-RUN apt-get install --no-install-recommends --no-upgrade -y \
+RUN apt-get update && apt-get install --no-install-recommends -y \
         git ca-certificates \
         make automake libtool pkg-config dpkg-dev valgrind qemu-user \
         gcc clang llvm libc6-dbg \
@@ -19,8 +18,20 @@ RUN apt-get install --no-install-recommends --no-upgrade -y \
         gcc-arm-linux-gnueabihf libc6-dev-armhf-cross libc6-dbg:armhf \
         gcc-aarch64-linux-gnu libc6-dev-arm64-cross libc6-dbg:arm64 \
         gcc-powerpc64le-linux-gnu libc6-dev-ppc64el-cross libc6-dbg:ppc64el \
-        wine gcc-mingw-w64-x86-64 \
+        gcc-mingw-w64-x86-64-win32 wine64 wine \
+        gcc-mingw-w64-i686-win32 wine32 \
         sagemath
 
-# Run a dummy command in wine to make it set up configuration
-RUN wine64-stable xcopy || true
+WORKDIR /root
+# The "wine" package provides a convience wrapper that we need
+RUN apt-get update && apt-get install --no-install-recommends -y \
+        git ca-certificates wine64 wine python3-simplejson python3-six msitools winbind procps && \
+    git clone https://github.com/mstorsjo/msvc-wine && \
+    mkdir /opt/msvc && \
+    python3 msvc-wine/vsdownload.py --accept-license --dest /opt/msvc Microsoft.VisualStudio.Workload.VCTools && \
+    msvc-wine/install.sh /opt/msvc
+
+# Initialize the wine environment. Wait until the wineserver process has
+# exited before closing the session, to avoid corrupting the wine prefix.
+RUN wine64 wineboot --init && \
+    while (ps -A | grep wineserver) > /dev/null; do sleep 1; done