Fix build order build policy docs

reference/commands/misc/graph.rst

@@ -110,7 +110,26 @@ which is the same as :command:`conan create|install`
   optional arguments:
     -h, --help            show this help message and exit
     -b [BUILD], --build [BUILD]
-                          nodes to build
+                          Optional, use it to choose if you want to build from
+                          sources: --build Build all from sources, do not use
+                          binary packages. --build=never Never build, use binary
+                          packages or fail if a binary package is not found.
+                          --build=missing Build from code if a binary package is
+                          not found. --build=cascade Will build from code all
+                          the nodes with some dependency being built (for any
+                          reason). Can be used together with any other build
+                          policy. Useful to make sure that any new change
+                          introduced in a dependency is incorporated by building
+                          again the package. --build=outdated Build from code if
+                          the binary is not built with the current recipe or
+                          when missing binary package. --build=[pattern] Build
+                          always these packages from source, but never build the
+                          others. Allows multiple --build parameters. 'pattern'
+                          is a fnmatch file pattern of a package reference.
+                          Default behavior: If you don't specify anything, it
+                          will be similar to '--build=never', but package
+                          recipes can override it with their 'build_policy'
+                          attribute in the conanfile.py.
     --json JSON           generate output file in json format