Add Universal Python testing script

README.txt

@@ -32,4 +32,15 @@ NOTES:
 
 - As of this commit: https://github.com/gregneagle/relocatable-python/commit/903c708a01d1a2444ea5648114f3acf6e7f94fd7, instead of removing the signature, we replace it with an ad-hoc signature. This is required for the code to actually run on Apple silicon.
 
-
+UNIVERSAL PYTHON
+
+As of Python 3.9.11 (Mar 16, 2022), Python.org offers a Universal Python build. If you want to test if your framework is also fully universal, you can use the included "python_universal_tester.sh" script. It takes your version of Python as an argument:
+```
+% ./python_universal_tester.sh 3.10
+Using Python 3.10
+All files are universal!
+% echo $?
+0
+```
+
+The script must be run from the same directory as the built Python.framework. If any files are not universal, it will list them and exit 1.

python_universal_tester.sh

@@ -0,0 +1,35 @@
+#!/bin/bash
+
+if [[ $1 == *"3."* ]]; then
+    echo "Using Python $1" 
+else
+    echo "Invalid Python version"
+    exit 1
+fi
+
+STATUS=0
+
+# ensure all .so and .dylibs are universal
+LIB_COUNT=$(find "Python.framework" -name "*.so" -or -name "*.dylib" | wc -l)
+UNIVERSAL_COUNT=$(find "Python.framework" -name "*.so" -or -name "*.dylib" | xargs file | grep "2 architectures" | wc -l)
+if [ "$LIB_COUNT" != "$UNIVERSAL_COUNT" ] ; then 
+    echo "$LIB_COUNT libraries (*.so and *.dylib) found in the framework; only $UNIVERSAL_COUNT are universal!"
+    echo "The following libraries are not universal:"
+    find Python.framework -name "*.so" -or -name "*.dylib" | xargs file | grep -v "2 architectures" | grep -v "(for architecture"
+    STATUS=1
+fi
+
+# test some more files in the framework
+MORE_FILES="Python.framework/Versions/$1/Resources/Python.app/Contents/MacOS/Python
+Python.framework/Versions/Current/Python
+Python.framework/Versions/Current/bin/python$1"
+
+for TESTFILE in $MORE_FILES ; do
+    ARCH_TEST=$(file "$TESTFILE" | grep "2 architectures")
+    if [ "$ARCH_TEST" == "" ]  ; then
+        echo "$TESTFILE is not universal!"
+        STATUS=1
+    fi
+done
+
+[[ $STATUS == 0 ]] && echo "All files are universal!" || exit $STATUS