Merge branch 'ci-msw-cross'

Add workflow for cross-building wxMSW on GitHub Actions.

build/tools/httpbin.sh

@@ -16,7 +16,9 @@ httpbin_launch() {
 
     case "$(uname -s)" in
         Linux)
-            dist_codename=$(lsb_release --codename --short)
+            if command -v lsb_release > /dev/null; then
+                dist_codename=$(lsb_release --codename --short)
+            fi
             ;;
 
         Darwin)
@@ -42,7 +44,7 @@ httpbin_launch() {
     esac
 
     # Ensure that we have at least some version of pip.
-    if ! python3 -m pip; then
+    if ! python3 -c 'import pip'; then
         sudo apt-get -q -o=Dpkg::Use-Pty=0 install python3-pip
     fi