Updated docs

Author: cmaglie

Diff for: cli/compile/compile.go

@@ -112,7 +112,7 @@ func NewCommand() *cobra.Command {
 	command.RegisterFlagCompletionFunc("programmer", func(cmd *cobra.Command, args []string, toComplete string) ([]string, cobra.ShellCompDirective) {
 		return arguments.GetInstalledProgrammers(), cobra.ShellCompDirectiveDefault
 	})
-	command.Flags().BoolVar(&compilationDatabaseOnly, "only-compilation-database", false, tr("Just produce the compilation database, without actually compiling."))
+	command.Flags().BoolVar(&compilationDatabaseOnly, "only-compilation-database", false, tr("Just produce the compilation database, without actually compiling. All build commands are skipped excecpt all the pre-* hooks."))
 	command.Flags().BoolVar(&clean, "clean", false, tr("Optional, cleanup the build folder and do not use any cached build."))
 	// We must use the following syntax for this flag since it's also bound to settings.
 	// This must be done because the value is set when the binding is accessed from viper. Accessing from cobra would only

Diff for: docs/platform-specification.md

@@ -399,6 +399,10 @@ recipe.hooks.sketch.prebuild.02.pattern=echo 2
 recipe.hooks.sketch.prebuild.11.pattern=echo 11
 ```
 
+Note: all the `pre*` hooks are executed also to produce the "compilation database" (it's a json file with the list of commands
+to run to compile the sketch), instead all the `post*` hooks and all compile commands will be skipped. See the
+[`arduino-cli compile`](commands/arduino-cli_compile.md) command for more info.
+
 ## Global platform.txt
 
 Properties defined in a platform.txt created in the **hardware** subfolder of the Arduino IDE installation folder will