build-python: Install a versionless python.exe in addition to python3.exe

This can make it marginally easier to use it, even if the embedded
Python installation isn't that much meant to be used for various
external purposes.

build-python.sh

@@ -159,4 +159,10 @@ $MAKE -j$CORES
 $MAKE install
 rm -rf $PREFIX/lib/python*/test
 find $PREFIX/lib/python* -name __pycache__ | xargs rm -rf
+
+# Provide a versionless executable as well; msys2 does something similar
+# (for python3, python3w, python3-config, idle3 and pydoc3) after installing
+# a Python version that is supposed to be the primary Python.
+cp -a $PREFIX/bin/python3.exe $PREFIX/bin/python.exe
+
 cd ../..