gcc

• Bootstrapping does not work in toolchain and in cross (only in native where it makes sense according to docs) (should be enabled by default in native, if not then explicitly pass --enable-bootstrap)
• bootstrap-lto-lean has to be used with make profiledbootstrap?
• bootstrap-debug-lean is slower and bigger compared to bootstrap-debug
• gcc bootstrap-lto build configuration adjusts CFLAGS and LDFLAGS
• --enable-link-mutex is deprecated, use --enable-link-serialization=1 instead: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109310 (=1 is sane, any higher value might thrash the system)
• cc1 depends on mpc at runtime
• Requires tar for the make target install-headers-tar