run-tests: Add busybox specific logic for figuring out what architectures we can execute

run-tests.sh

@@ -156,6 +156,19 @@ if [ -z "$RUN_X86_64" ] && [ -z "$RUN_I686" ] && [ -z "$RUN_ARMV7" ] && [ -z "$R
             set_native x86_64
         fi
         ;;
+    Windows_NT) # Busybox
+        case $(uname -m) in
+        i386|i686|x86_64)
+            # Assume that any current x86 machine is capable of running 64 bit
+            # binaries.
+            set_native x86_64
+            ;;
+        armv7|aarch64)
+            # Busybox uname -v prints the plain build number, like "22000".
+            set_native aarch64 "$(uname -v)"
+            ;;
+        esac
+        ;;
     Linux)
         if [ -e /proc/sys/fs/binfmt_misc/WSLInterop ]; then
             # On WSL, inspect the architecture and build number.