Compiling software with same options

[Lanoxx]

Hi,

I have a question regarding the options that are used to build the 
source code of a package, there are often some options that can be 
passed to either ./autogen.sh or ./configure which influence what module 
are build or how a libarary or program is build. How can I find out 
which options were used originally when the package was build by Ubuntu?

For example I would like to rebuild the glib2.0-x source from Ubuntu 
12.10 with a small patch. I have already downloaded patched and compiled 
the Ubuntu source of glib2.0 with:

apt-get source glib2.0-...
//apply patch ...
./autogen.sh --prefix=/opt/... && make && sudo make install

And now I want to compile and install it into the prefix=/usr for fix 
the bug on the system.

However given that glib is quite an essential library I am a bit afraid 
that I am forgetting some important options and that something might be 
broken afterwards. Could anyone give me a hint how to properly compile 
this package?

Regards