Revert "Remove tempfile usage from test_sanity.py. NFC" (#25625)

Reverts #25617

The tests in question did not pass. Reverting while I figure out what
happened here.

Author: sbc100

test/test_sanity.py

@@ -5,13 +5,16 @@
 
 import glob
 import os
+import platform
 import re
 import shutil
 import stat
+import tempfile
 import time
 from pathlib import Path
 from subprocess import PIPE, STDOUT
 
+import common
 from common import (
   EMBUILDER,
   RunnerCore,
@@ -177,31 +180,32 @@ def test_aaa_normal(self):
 
   @with_env_modify({'EM_CONFIG': None})
   def test_firstrun(self):
-    default_config = EM_CONFIG
+    default_config = path_from_root('.emscripten')
     output = self.do([EMCC, '-v'])
     self.assertContained('emcc: warning: config file not found: %s.  You can create one by hand or run `emcc --generate-config`' % default_config, output)
 
-    temp_bin = os.path.abspath('bin')
-    os.mkdir(temp_bin)
-
-    def make_new_executable(name):
-      utils.write_file(os.path.join(temp_bin, name), '')
-      make_executable(os.path.join(temp_bin, name))
+    try:
+      temp_bin = tempfile.mkdtemp()
 
-    make_new_executable('wasm-ld')
-    make_new_executable('node')
+      def make_new_executable(name):
+        utils.write_file(os.path.join(temp_bin, name), '')
+        make_executable(os.path.join(temp_bin, name))
 
-    with env_modify({'PATH': temp_bin + os.pathsep + os.environ['PATH']}):
-      output = self.do([EMCC, '--generate-config'])
+      make_new_executable('wasm-ld')
+      make_new_executable('node')
 
-    config_data = utils.read_file(default_config)
+      with env_modify({'PATH': temp_bin + os.pathsep + os.environ['PATH']}):
+        output = self.do([EMCC, '--generate-config'])
+    finally:
+      shutil.rmtree(temp_bin)
+      config_data = utils.read_file(default_config)
 
     self.assertContained('An Emscripten settings file has been generated at:', output)
     self.assertContained(default_config, output)
     self.assertContained('It contains our best guesses for the important paths, which are:', output)
     self.assertContained('LLVM_ROOT', output)
     self.assertContained('NODE_JS', output)
-    if not utils.WINDOWS:
+    if platform.system() != 'Windows':
       # os.chmod can't make files executable on Windows
       self.assertIdentical(temp_bin, re.search("^ *LLVM_ROOT *= (.*)$", output, re.M).group(1))
       possible_nodes = [os.path.join(temp_bin, 'node')]
@@ -520,13 +524,29 @@ def test_emcc_cache_flag(self, use_response_files, relative):
 
   def test_emconfig(self):
     restore_and_set_up()
-    create_file('custom_config', get_basic_config())
+
+    fd, custom_config_filename = tempfile.mkstemp(prefix='.emscripten_config_')
+
+    orig_config = utils.read_file(EM_CONFIG)
+
+    # Move the ~/.emscripten to a custom location.
+    with os.fdopen(fd, "w") as f:
+      f.write(get_basic_config())
 
     # Make a syntax error in the original config file so that attempting to access it would fail.
-    utils.write_file(EM_CONFIG, 'asdfasdfasdfasdf\n')
+    utils.write_file(EM_CONFIG, 'asdfasdfasdfasdf\n\'\'\'' + orig_config)
+
+    temp_dir = tempfile.mkdtemp(prefix='emscripten_temp_')
+
+    with common.chdir(temp_dir):
+      self.run_process([EMCC, '--em-config', custom_config_filename] + MINIMAL_HELLO_WORLD + ['-O2'])
+      result = self.run_js('a.out.js')
+
+    self.assertContained('hello, world!', result)
 
-    self.run_process([EMCC, '--em-config', 'custom_config'] + MINIMAL_HELLO_WORLD)
-    self.assertContained('hello, world!', self.run_js('a.out.js'))
+    # Clean up created temp files.
+    os.remove(custom_config_filename)
+    shutil.rmtree(temp_dir)
 
   def test_emcc_ports(self):
     restore_and_set_up()