Update GUIDELINES.md

GUIDELINES.md

@@ -110,6 +110,8 @@ and compilers (e.g., `gcc`) should be specified in the build requirements.
 * example requiring `autoconf`: [srprism](recipes/srprism)
 * simple example: [samtools](recipes/samtools)
 
+If your package links dynamically against a particular library, it is often necessary to pin the version against which it was compiled, in order to avoid ABI incompatibilities. Instead of hardcoding a particular version in the recipe, we use jinja templates to achieve this. For example, bioconda provides an environnmnet variable `CONDA_BOOST` that contains the current major version of boost. You should pin your boost dependency against that version. An example is the [salmon recipe](recipes/salmon). If you need to pin another library, please notify @bioconda/core, and we will set up a corresponding environment variable.
+
 ## General command-line tools
 If a command-line tool is installed, it should be tested. If it has a shebang
 line, it should be patched to use `/usr/bin/env` for more general use.