Update GUIDELINES.md (bioconda#1575)

GUIDELINES.md

@@ -110,7 +110,7 @@ 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.
+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). You find the libraries you can currently pin in [scripts/env_matrix.yml](https://github.com/bioconda/bioconda-recipes/blob/master/scripts/env_matrix.yml). 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