Build fails with LTO

[eli-schwartz]

I tried to build with these flags: -flto=4 -Werror=odr -Werror=lto-type-mismatch -Werror=strict-aliasing

I got this compile error:

x86_64-pc-linux-gnu-g++  -march=native -fstack-protector-all -O2 -pipe -fdiagnostics-color=always -frecord-gcc-switches -U_FORTIFY_SOURCE -D_FORTIFY_SOURCE=3 -fstack-clash-protection -flto=4 -Werror=odr -Werror=lto-type-mismatch -Werror=strict-aliasing  -Wformat -Werror=format-security -fno-rtti -fno-exceptions -W -Wall  -Wl,-O1 -Wl,--as-needed -flto=4 -Werror=odr -Werror=lto-type-mismatch -Werror=strict-aliasing -Wl,--defsym=__gentoo_check_ldflags__=0 -o nullmailer-smtpd smtpd.o ../lib/libnullmailer.a 
../lib/cli++/cli++.h:35:20: error: ‘cli_program’ violates the C++ One Definition Rule [-Werror=odr]
   35 | extern const char* cli_program;
      |                    ^
smtpd.cc:55:19: note: ‘cli_program’ was previously declared here
   55 | extern const char cli_program[] = "nullmailer-smtpd";
      |                   ^
lto1: some warnings being treated as errors
lto-wrapper: fatal error: x86_64-pc-linux-gnu-g++ returned 1 exit status

Downstream report: https://bugs.gentoo.org/859529
Full build logs: build.log