When building the recent mainline JDK (26), I see the following warning messages:

warning: (arm64) /tmp/lto.o unable to open object file: No such file or directory
warning: no debug symbols in executable (-arch arm64)

The build completes normally even with these warnings.

I am on macos aarch64, but I see the same warning on macos x64 and aarch64 in our CI.

This could be related to the recent change integrated through JDK-8370438.