Add some information to Packaging cmake wiki

[Rex Dieter]

Kevin Kofler wrote:

> Richard Shaw wrote:
>> I've noticed with several packages lately that frequently the wrong
>> build flags are used or appened to the ones the cmake macro sets.
>> Sometimes this can happen because the main cmake configuration file
>> forces the type to "Release" (bad!) but not always.
>> 
>> I've found that adding: "-DCMAKE_RELEASE_TYPE=RelWithDebinfo" often
>> takes care of this.
> 
> FYI, some packages use bad flags with RelWithDebinfo and good ones with
> Release, some always use good flags, and some always use bad flags (and
> have to be patched).
> 
> (For example, the KDE packages are all built in release mode.)
> 
> It depends on the package. Always check the CFLAGS being used (the verbose
> build output).

I sympathize with Richard's sentiment that we should make an effort to 
sanitize and ideally standarize this in our builds... and using 
RelWithDebinfo CMAKE_RELEASE_TYPE is one approach to achieving that.

-- rex