gcc

Disable bootstrap; stage1 is good enough
Use a different libexecdir
bootstrap-lto build configuration adjusts CFLAGS and LDFLAGS
bootstrap-lto-lean has to be used with make profiledbootstrap
bootstrap-debug-lean is slower and bigger compared to bootstrap-debug
BOOT_CFLAGS, BOOT_LDFLAGS and --with-boot-ldflags only make sense when bootstrapping gcc; applies to stages 2 and 3
LD_FOR_TARGET, STAGE1_CFLAGS and STAGE1_LDFLAGS apply to stage 1
--enable-link-mutex has been 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 run time
Depends on tar for the make target install-headers-tar
As of 14.1, new configure options --enable-host-pie, to build the compiler executables as PIE; and --enable-host-bind-now, to link the compiler executables with -Wl,-z,now to enable additional hardening
--enable-host-shared has a performance penalty on gcc
Might need a lex/flex library libfl.a:

checking for lex library... not found
configure: WARNING: required lex library not found; giving up on touch lex.yy.c

BOOT_CXXFLAGS has been deprecated
CFLAGS, CXXFLAGS, CFLAGS_FOR_TARGET and CXXFLAGS_FOR_TARGET are being picked up from the environment; the latter two are automatically assigned to the former two
Check clocale to use for libstdc++; generic vs --disable-clocale?
libgcc_s.so.1 size dramatically reduced when using stage1 flags (from ~ 830k to ~ 170k)
otool is for mach os, and is part of LLVM; the otool not found error is normal for gcc
Move cpp from lib to bin?

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