Can have multiple source files with the same name in one target.

backends.py

@@ -878,7 +878,8 @@ class NinjaBackend(Backend):
             src_filename = os.path.basename(src)
         else:
             src_filename = src
-        rel_obj = os.path.join(self.get_target_private_dir(target), os.path.basename(src_filename))
+        obj_basename = src_filename.replace('/', '_').replace('\\', '_')
+        rel_obj = os.path.join(self.get_target_private_dir(target), obj_basename)
         rel_obj += '.' + self.environment.get_object_suffix()
         dep_file = rel_obj + '.' + compiler.get_depfile_suffix()
         if self.environment.coredata.use_pch:

test cases/common/54 same file name/d1/file.c

@@ -0,0 +1 @@
+int func1() { return 42; }

test cases/common/54 same file name/d2/file.c

@@ -0,0 +1 @@
+int func2() { return 42; }

test cases/common/54 same file name/meson.build

@@ -0,0 +1,3 @@
+project('samefile', 'c')
+
+test('basic', executable('prog', 'prog.c', 'd1/file.c', 'd2/file.c'))

test cases/common/54 same file name/prog.c

@@ -0,0 +1,6 @@
+int func1();
+int func2();
+
+int main(int argc, char **argv) {
+    return func1() - func2();
+}