Use python3 explicitly. (#5540)

Some Linux images don't ship with a plain 'python'

test/scripts/test_compact_ids.py

@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 # Copyright (c) 2017 Google Inc.
 
 # Licensed under the Apache License, Version 2.0 (the "License");
@@ -47,7 +47,7 @@ def print_usage():
   template= \
 """{script} tests correctness of opt pass tools/opt --compact-ids
 
-USAGE: python {script} [<spirv_files>]
+USAGE: python3 {script} [<spirv_files>]
 
 Requires tools/spirv-dis, tools/spirv-as and tools/spirv-opt to be in path
 (call the script from the SPIRV-Tools build output directory).

utils/check_copyright.py

@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 # coding=utf-8
 # Copyright (c) 2016 Google Inc.
 #

utils/check_symbol_exports.py

@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 # Copyright (c) 2017 Google Inc.
 
 # Licensed under the Apache License, Version 2.0 (the "License");

utils/fixup_fuzz_result.py

@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 # Copyright (c) 2018 Google Inc.
 #
 # Licensed under the Apache License, Version 2.0 (the "License");

utils/generate_changelog.py

@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 
 # Copyright (c) 2023 Google Inc.
 #

utils/generate_grammar_tables.py

@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 # Copyright (c) 2016 Google Inc.
 
 # Licensed under the Apache License, Version 2.0 (the "License");

utils/generate_registry_tables.py

@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 # Copyright (c) 2016 Google Inc.
 
 # Licensed under the Apache License, Version 2.0 (the "License");

utils/generate_vim_syntax.py

@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 # Copyright (c) 2016 Google Inc.
 
 # Licensed under the Apache License, Version 2.0 (the "License");

utils/update_build_version.py

@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 
 # Copyright (c) 2016 Google Inc.
 #