Add SAST documentation on SELinux support

doc/user/application_security/sast/analyzers.md

@@ -54,6 +54,7 @@ support the following features:
 - [Multi-project support](index.md#multi-project-support)
 - [Offline support](index.md#running-sast-in-an-offline-environment)
 - [Emits JSON report format](index.md#reports-json-format)
+- [SELinux support](index.md#running-sast-in-selinux)
 
 ## Official default analyzers
 

doc/user/application_security/sast/index.md

@@ -707,6 +707,10 @@ offline environment, certificate verification with an external source is not pos
 self-signed certificate or disable certificate verification. Refer to the package manager's
 documentation for instructions.
 
+## Running SAST in SELinux
+
+By default SAST analyzers are supported in GitLab instances hosted on SELinux. Adding a `before_script` in an [overriden SAST job](#overriding-sast-jobs) may not work as runners hosted on SELinux have restricted permissions.
+
 ## Troubleshooting
 
 ### SAST debug logging