Build musl 'exit' files by default. NFC (#26083)

Previously we were by default excluding the `exit` directory and then
including and explict subset.

Now we include the whole directory and exclude the files we don't want.
The overall file list should be the same before and after. Hence NFC.

Author: sbc100

tools/system_libs.py

@@ -492,6 +492,7 @@ def build_objects(self, build_dir):
     batches = {}
     commands = []
     objects = set()
+    objects_lowercase = set()
     cflags = self.get_cflags()
     for src in self.get_files():
       ext = utils.suffix(src)
@@ -509,17 +510,17 @@ def build_objects(self, build_dir):
         cmd += cflags
       cmd = self.customize_build_cmd(cmd, src)
 
-      object_basename = utils.unsuffixed_basename(src).lower()
+      object_basename = utils.unsuffixed_basename(src)
       o = os.path.join(build_dir, object_basename + '.o')
-      if o in objects:
+      if o.lower() in objects_lowercase:
         # If we have seen a file with the same name before, we need a separate
         # command to compile this file with a custom unique output object
         # filename, as batch compile doesn't allow such customization.
         #
         # This is needed to handle, for example, _exit.o and _Exit.o.
         object_uuid = 0
         # Find a unique basename
-        while o in objects:
+        while o.lower() in objects_lowercase:
           object_uuid += 1
           o = os.path.join(build_dir, f'{object_basename}__{object_uuid}.o')
         commands.append(cmd + [src, '-o', o])
@@ -529,11 +530,10 @@ def build_objects(self, build_dir):
         src = os.path.relpath(src, build_dir)
         src = utils.normalize_path(src)
         batches.setdefault(tuple(cmd), []).append(src)
-        # No -o in command, use original file name.
-        o = os.path.join(build_dir, utils.unsuffixed_basename(src) + '.o')
       else:
         commands.append(cmd + [src, '-o', o])
       objects.add(o)
+      objects_lowercase.add(o.lower())
 
     if batch_inputs:
       # Choose a chunk size that is large enough to avoid too many subprocesses
@@ -1144,7 +1144,7 @@ def get_files(self):
     # musl modules
     ignore = [
         'ipc', 'passwd', 'signal', 'sched', 'time', 'linux',
-        'aio', 'exit', 'legacy', 'mq', 'setjmp',
+        'aio', 'legacy', 'mq', 'setjmp',
         'ldso', 'malloc',
     ]
 
@@ -1158,11 +1158,13 @@ def get_files(self):
         'getgrouplist.c', 'initgroups.c', 'wordexp.c', 'timer_create.c',
         'getauxval.c',
         'lookup_name.c',
-        # 'process' exclusion
+        # 'process' exclusions
         'fork.c', 'vfork.c', 'posix_spawn.c', 'posix_spawnp.c', 'execve.c', 'waitid.c', 'system.c',
         '_Fork.c',
-        # 'env' exclusion
+        # 'env' exclusions
         '__reset_tls.c', '__init_tls.c', '__libc_start_main.c',
+        # 'exit' exclusions
+        'assert.c', 'exit.c',
     ]
 
     ignore += LIBC_SOCKETS
@@ -1312,10 +1314,6 @@ def get_files(self):
         path='system/lib/libc/musl/src/sched',
         filenames=['sched_yield.c'])
 
-    libc_files += files_in_path(
-        path='system/lib/libc/musl/src/exit',
-        filenames=['abort.c', '_Exit.c', 'atexit.c', 'at_quick_exit.c', 'quick_exit.c'])
-
     libc_files += files_in_path(
         path='system/lib/libc/musl/src/ldso',
         filenames=['dladdr.c', 'dlerror.c', 'dlsym.c', 'dlclose.c'])