GHS: GHSMULTI - Update documentation to match implementation

* The variable being set was named `GHSMULTI` not `GHS-MULTI`.

Auxiliary/vim/syntax/cmake.vim

@@ -1903,7 +1903,7 @@ syn keyword cmakeVariable contained
             \ DOXYGEN_XML_PROGRAMLISTING
             \ ENV
             \ EXECUTABLE_OUTPUT_PATH
-            \ GHS-MULTI
+            \ GHSMULTI
             \ IOS
             \ LIBRARY_OUTPUT_PATH
             \ MINGW

Help/manual/cmake-variables.7.rst

@@ -308,7 +308,7 @@ Variables that Describe the System
    /variable/CMAKE_SYSTEM_PROCESSOR
    /variable/CMAKE_SYSTEM_VERSION
    /variable/CYGWIN
-   /variable/GHS-MULTI
+   /variable/GHSMULTI
    /variable/IOS
    /variable/MINGW
    /variable/MSVC

Help/variable/GHS-MULTI.rst

@@ -1,6 +0,0 @@
-GHS-MULTI
----------
-
-.. versionadded:: 3.3
-
-``True`` when using :generator:`Green Hills MULTI` generator.

Help/variable/GHSMULTI.rst

@@ -0,0 +1,9 @@
+GHSMULTI
+--------
+
+.. versionadded:: 3.3
+
+``1`` when using :generator:`Green Hills MULTI` generator.
+
+Also, Set to ``1`` when the target system is a Green Hills platform
+(i.e. When CMAKE_SYSTEM_NAME is ``GHS-MULTI``).