The flag --with-private-namespace is ignored when building with GCC with LTO enabled

[sfc-gh-tmarzec]

In my project, I'm using two copies of jemalloc simultaneously. To avoid duplicated symbols, one of then modifies the symbols using --with-jemalloc-prefix and --with-private-namespace flags.

When building with LTO, the --with-private-namespace flag has no effect, but no errors/warnings are reported.
I was able to track this problem, and it turns out that jemalloc calls nm in its post-processing step used for renaming private symbols. This fails when using LTO and building with GCC, in which case it's necessary to use gcc-nm instead of nm. I was able to fix this by manually setting the NM env variable to the path of gcc-nm.

The issue I see here is that this behaviour is not documented anywhere, and the errors returned by nm seem to be ignored (and not reported to the user).