[compiler-rt][builtins] Add compiler flags to catch potential errors

[compiler-rt][builtins] Add compiler flags to catch potential errors
that can lead to security vulnerabilities

Also, fix a few places that were causing -Wshadow and
-Wformat-nonliteral warnings to be emitted.

This reapplies the patch that was reverted in caaafe4ae250 because it
broke Fuchsia builders.

I reverted the changes I made to InstrProfData.inc and instead renamed
the variables in InstrProfilingWriter.c. Also fixed a bug in function
add_security_warnings that was causing it to pass -Wformat-nonliteral
when the compiler doesn't support it.