As explained elsewhere (see The GNU Autoconf Manual), any package needs configuration at build-time. If your package uses Guile (or uses a package that in turn uses Guile), you probably need to know what specific Guile features are available and details about them.
The way to do this is to write feature tests and arrange for their execution
by the configure script, typically by adding the tests to
configure.ac, and running
autoconf to create configure.
Users of your package then run configure in the normal way.
Macros are a way to make common feature tests easy to express. Autoconf provides a wide range of macros (see Existing Tests), and Guile installation provides Guile-specific tests in the areas of: program detection, compilation flags reporting, and Scheme module checks.