Sublime: Add option to specify env vars for the .sublime-project

Create a `CMAKE_SUBLIME_TEXT_2_ENV_SETTINGS` variable to control
addition of env vars in the `.sublime-project`.

Closes: #16387

Help/manual/cmake-variables.7.rst

@@ -160,6 +160,7 @@ Variables that Change Behavior
    /variable/CMAKE_PROJECT_PROJECT-NAME_INCLUDE
    /variable/CMAKE_SKIP_INSTALL_ALL_DEPENDENCY
    /variable/CMAKE_STAGING_PREFIX
+   /variable/CMAKE_SUBLIME_TEXT_2_ENV_SETTINGS
    /variable/CMAKE_SUBLIME_TEXT_2_EXCLUDE_BUILD_TREE
    /variable/CMAKE_SYSTEM_APPBUNDLE_PATH
    /variable/CMAKE_SYSTEM_FRAMEWORK_PATH

Help/release/dev/st2-env-settings.rst

@@ -0,0 +1,6 @@
+st2-env-settings
+----------------
+
+* The :generator:`Sublime Text 2` extra generator learned to place
+  environment variables in the generated ``.sublime-project``.
+  See the :variable:`CMAKE_SUBLIME_TEXT_2_ENV_SETTINGS` variable.

Help/variable/CMAKE_SUBLIME_TEXT_2_ENV_SETTINGS.rst

@@ -0,0 +1,25 @@
+CMAKE_SUBLIME_TEXT_2_ENV_SETTINGS
+---------------------------------
+
+This variable contains a list of env vars as a list of tokens with the
+syntax ``var=value``.
+
+Example:
+
+.. code-block:: cmake
+
+  set(CMAKE_SUBLIME_TEXT_2_ENV_SETTINGS
+     "FOO=FOO1\;FOO2\;FOON"
+     "BAR=BAR1\;BAR2\;BARN"
+     "BAZ=BAZ1\;BAZ2\;BAZN"
+     "FOOBAR=FOOBAR1\;FOOBAR2\;FOOBARN"
+     "VALID="
+     )
+
+In case of malformed variables CMake will fail:
+
+.. code-block:: cmake
+
+  set(CMAKE_SUBLIME_TEXT_2_ENV_SETTINGS
+      "THIS_IS_NOT_VALID"
+      )