Produce a basic Windows installer package

We're very early adopters of msitools' new UI feature,
so this doesn't work on MSYS2 directly yet due to an old version.

meson.build

@@ -338,6 +338,19 @@ elif meson.is_cross_build()
 	msys2_root = meson.get_external_property('msys2_root')
 	meson.add_install_script('msys2-install.sh', msys2_root)
 
+	# TODO: If we used DESTDIR instead of the prefix, this could probably
+	# be a custom target that invokes "meson install --destdir $(pwd)/package"
+	# through "meson compile -C builddir msi". Try it out, also in MSYS2.
+	meson.add_install_script('msys2-package.sh', host_machine.cpu())
+	configure_file(
+		input : 'fiv.wxs.in',
+		output : 'fiv.wxs',
+		configuration : configuration_data({
+			'ProjectName' : meson.project_name(),
+			'ProjectVersion' : meson.project_version(),
+		}),
+	)
+
 	# This is the minimum to run targets from msys2-configure.sh builds.
 	meson.add_devenv({
 		'WINEPATH' : msys2_root / 'bin',