Fixes and constrained suppression of compiler warnings

[jbcoe]

• Suppress target-specific compiler warnings for non-MSVC builds

• Fix format specifier in error message

[StephenOman]

What is the purpose of limiting the noisy warning suppression to non-MVSC?

[jbcoe]

I don't think that the suppressions I have specified will work on MSVC.

We could consider

target_compile_options(makedefs PRIVATE 
    $<$<CXX_COMPILER_ID:MSVC>:/wd4996>
    $<$<NOT:$<CXX_COMPILER_ID:MSVC>>:-Wno-deprecated-non-prototype>
)

(or equivalent) as I think that MSVC will likely treat -Wno-deprecated-non-prototype as an unknown command-line option and trigger an error (or a warning about an invalid argument).

I don't have access to MSVC to be able to check.