GNUInstallDirs.cmake: Various improvements

- Integrate
  c07bba2730 (diff-1e2deb5301e9481203102fcddd1b2d0d2bf0ddc1cbb445c7f4b6414a3b869ce8)
  so that the default man directory is <CMAKE_INSTALL_PREFIX>/share/man
  on FreeBSD systems.

- For good measure, integrate
  f835f189ae
  so that the default info directory is
  <CMAKE_INSTALL_PREFIX>/share/info on FreeBSD systems, even though we
  don't use that directory.

- Automatically set the CMake variable type to PATH for any
  user-specified CMAKE_INSTALL_*DIR variables.

Addresses concerns raised in #326, #346, #648

Closes #648

BUILDING.md

@@ -605,15 +605,6 @@ brackets, then its final value will depend on the final value of that other
 variable.  For instance, the default value of `CMAKE_INSTALL_MANDIR` is
 **\<CMAKE\_INSTALL\_DATAROOTDIR\>/man**.
 
-NOTE: If setting one of these directory variables to a relative path using the
-CMake command line, you must specify that the variable is of type `PATH`.
-For example:
-
-    cmake -G"{generator type}" -DCMAKE_INSTALL_LIBDIR:PATH=lib {source_directory}
-
-Otherwise, CMake will assume that the path is relative to the build directory
-rather than the install directory.
-
 
 Creating Distribution Packages
 ==============================

cmakescripts/GNUInstallDirs.cmake

@@ -118,9 +118,10 @@
 #   absolute paths where necessary, using the same logic.
 
 #=============================================================================
+# Copyright 2018 Tobias C. Berner
 # Copyright 2018 Matthias Räncker
-# Copyright 2016, 2019 D. R. Commander
-# Copyright 2016 Dmitry Marakasov
+# Copyright 2016, 2019, 2024 D. R. Commander
+# Copyright 2016, 2021 Dmitry Marakasov
 # Copyright 2016 Roger Leigh
 # Copyright 2015 Alex Turbov
 # Copyright 2014 Rolf Eike Beer
@@ -181,6 +182,10 @@ macro(GNUInstallDirs_set_install_dir var docstring)
     set(_GNUInstallDirs_CMAKE_INSTALL_FORCE_${var} "FORCE")
   endif()
 
+  if(DEFINED CMAKE_INSTALL_${var} AND NOT CMAKE_INSTALL_${var} MATCHES "^/")
+    set_property(CACHE CMAKE_INSTALL_${var} PROPERTY TYPE PATH)
+  endif()
+
   set(CMAKE_INSTALL_${var} "${CMAKE_INSTALL_DEFAULT_${var}}" CACHE PATH
     "${docstring} (Default: ${CMAKE_INSTALL_DEFAULT_${var}})"
     ${_GNUInstallDirs_CMAKE_INSTALL_FORCE_${var}})
@@ -300,7 +305,7 @@ GNUInstallDirs_set_install_dir(DATADIR
   "The directory under which read-only architecture-independent data files should be installed")
 
 if(NOT DEFINED CMAKE_INSTALL_DEFAULT_INFODIR)
-  if(CMAKE_SYSTEM_NAME MATCHES "^(.*BSD|DragonFly)$")
+  if(CMAKE_SYSTEM_NAME MATCHES "^(([^kF].*)?BSD|DragonFly)$")
     set(CMAKE_INSTALL_DEFAULT_INFODIR "info")
   else()
     set(CMAKE_INSTALL_DEFAULT_INFODIR "<CMAKE_INSTALL_DATAROOTDIR>/info")
@@ -310,7 +315,7 @@ GNUInstallDirs_set_install_dir(INFODIR
   "The directory into which info documentation files should be installed")
 
 if(NOT DEFINED CMAKE_INSTALL_DEFAULT_MANDIR)
-  if(CMAKE_SYSTEM_NAME MATCHES "^(.*BSD|DragonFly)$")
+  if(CMAKE_SYSTEM_NAME MATCHES "^(([^k].*)?BSD|DragonFly)$" AND NOT CMAKE_SYSTEM_NAME MATCHES "^(FreeBSD)$")
     set(CMAKE_INSTALL_DEFAULT_MANDIR "man")
   else()
     set(CMAKE_INSTALL_DEFAULT_MANDIR "<CMAKE_INSTALL_DATAROOTDIR>/man")