PGO: compiler warnings for source files with no profile data about cpython

[erlend-aasland]

Seems easy enough to add the suppression to CFLAGS manually, yeah? Should we just doc it?

I would be fine with that.

[zooba]

It's one of these cases where if we suppress them once, we'll forget about coverage entirely, which is worse than simply continuing to not fix it (someone might be motivated to fix it in the future if they see it)

[zooba]

Unless they're actually disruptive (breaking builds), I'd rather leave them there by default.

Seems easy enough to add the suppression to CFLAGS manually, yeah? Should we just doc it?

[erlend-aasland]

Example warning:

gcc -bundle -undefined dynamic_lookup      Modules/syslogmodule.o   -o Modules/syslog.cpython-313-darwin.so
gcc  -fno-strict-overflow -Wsign-compare -Wunreachable-code -DNDEBUG -g -O3 -Wall    -std=c11 -Wextra -Wno-unused-parameter -Wno-missing-field-initializers -Wstrict-prototypes -Werror=implicit-function-declaration -fvisibility=hidden -fprofile-instr-use=/Users/erlend.aasland/src/python/build-main/code.profclangd -I../main/Include/internal -I../main/Include/internal/mimalloc -IObjects -IInclude -IPython -I. -I../main/Include     -c ../main/Modules/termios.c -o Modules/termios.o
warning: no profile data available for file "termios.c" [-Wprofile-instr-unprofiled]