Save extension build objects in unique directories.

When C coverage is enabled, the path to the object file is saved. Since
we re-use source files in multiple extensions, libgcov will complain at
runtime that it is trying to save coverage for the same object file at
different timestamps (since each source is compiled again for each
extension). Thus, we need to use unique temporary build directories to
store object files for each extension.

Author: QuLogic

setup.py

@@ -192,6 +192,20 @@ def build_extensions(self):
             package.do_custom_build(env)
         return super().build_extensions()
 
+    def build_extension(self, ext):
+        # When C coverage is enabled, the path to the object file is saved.
+        # Since we re-use source files in multiple extensions, libgcov will
+        # complain at runtime that it is trying to save coverage for the same
+        # object file at different timestamps (since each source is compiled
+        # again for each extension). Thus, we need to use unique temporary
+        # build directories to store object files for each extension.
+        orig_build_temp = self.build_temp
+        self.build_temp = os.path.join(self.build_temp, ext.name)
+        try:
+            super().build_extension(ext)
+        finally:
+            self.build_temp = orig_build_temp
+
 
 def update_matplotlibrc(path):
     # If packagers want to change the default backend, insert a `#backend: ...`