Utils: Add documentation for Environment::originalSystemEnvironment()

Change-Id: I7791f0b111f5728bd21d2870d6a6793b433d9b37
Reviewed-by: Marcus Tillmanns <marcus.tillmanns@qt.io>

src/libs/utils/environment.cpp

@@ -200,6 +200,8 @@ void Environment::prependOrSetLibrarySearchPaths(const FilePaths &values)
     This can be different from the system environment that \QC started in if the
     user changed it in \uicontrol Preferences > \uicontrol Environment >
     \uicontrol System > \uicontrol Environment.
+
+    \sa originalSystemEnvironment()
 */
 
 Environment Environment::systemEnvironment()
@@ -208,6 +210,17 @@ Environment Environment::systemEnvironment()
     return *staticSystemEnvironment();
 }
 
+/*!
+    Returns \QC's original system environment.
+
+    This is the full, unmodified environment that \QC was started with.
+    Use this environment to start processes that are built alongside \QC
+    and thus have the same library dependencies. This is particularly
+    relevant if \QC was started via Squish or another instance of \QC,
+    i.e. in testing or development contexts.
+    For all other processes, use \l systemEnvironment() or more specialized
+    variants such as the build environment, if applicable.
+*/
 const Environment &Environment::originalSystemEnvironment()
 {
     static const Environment env(QProcessEnvironment::systemEnvironment().toStringList());