Merge topic 'GNUInstallDirs-arch-linux'

18365587c8 GNUInstallDirs: Keep 'lib' as default LIBDIR on Arch Linux based systems

Acked-by: Kitware Robot <[email protected]>
Merge-request: !3735

Modules/GNUInstallDirs.cmake

@@ -222,7 +222,8 @@ if(NOT DEFINED CMAKE_INSTALL_LIBDIR OR (_libdir_set
     # updated to the new default, unless the user explicitly changed it.
   endif()
   if(CMAKE_SYSTEM_NAME MATCHES "^(Linux|kFreeBSD|GNU)$"
-      AND NOT CMAKE_CROSSCOMPILING)
+      AND NOT CMAKE_CROSSCOMPILING
+      AND NOT EXISTS "/etc/arch-release")
     if (EXISTS "/etc/debian_version") # is this a debian system ?
       if(CMAKE_LIBRARY_ARCHITECTURE)
         if("${CMAKE_INSTALL_PREFIX}" MATCHES "^/usr/?$")