fix(build): handle read-only source tree in PEP 517 builds

get_version() writes RELEASE-VERSION which fails when pip runs
setup.py in build isolation with a read-only source copy.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: flound1129

version.py

@@ -42,8 +42,11 @@
 def get_version():
     version = '%s.dev%d' % (BASE_VERSION, int(time.time()))
 
-    with open(VERSION_FILE, 'w') as f:
-        f.write('%s\n' % version)
+    try:
+        with open(VERSION_FILE, 'w') as f:
+            f.write('%s\n' % version)
+    except OSError:
+        pass
 
     return version