Add test, shell for windows

.github/workflows/wheels/cibw_before_build.sh

@@ -0,0 +1,30 @@
+set -e
+set -x
+
+# Don't use objects from previous compiles on Windows/macOS
+make clean
+
+# DEBUG: show python3 and python3-config outputs
+python3 --version
+python3-config --includes
+
+# Build boost
+cd ./boost
+## Delete the artefacts from previous builds (if any)
+rm -rf ./pfx
+## Bootstrap bjam
+./bootstrap.sh --prefix=./pfx
+## Build Boost against current version of Python, only for
+## static linkage (Boost is statically linked because system boost packages
+## wildly vary in versions, including the libboost_python3 version)
+./b2\
+    -j$(getconf _NPROCESSORS_ONLN 2>/dev/null || sysctl -n hw.ncpu)\
+    --prefix=./pfx\
+    --with-filesystem\
+    --with-system\
+    --with-python\
+    cxxflags="$(python3-config --includes) -std=c++17 -fPIC"\
+    cflags="$(python3-config --includes) -fPIC"\
+    link=static\
+    variant=release\
+    install