The first part of this patch fixes the PR, we should be adding
target-libstdc++-v3 to noconfigdirs, not libstdc++-v3.
The second part disables the target libs that can't be bootstrapped
without libstdc++.
libcilkrts and libsanitizer use lots of std:: stuff.
libitm only uses std::atomic, but in any case fails to build when
--disable-libstdcxx is used, with this error:
xg++: error: unrecognized command line option ‘-funconfigured-libstdc++-v3’
Bootstrapped with and without --disable-libstdcxx and tested on
x86_64-linux.
PR libstdc++/61011
* configure.ac (--disable-libstdcxx): Set noconfigdirs correctly.
Disable libcilkrts, libitm, libsanitizer when not building libstdc++.
* configure: Regenerate.
OK for trunk?
