Revert "cmake: 3.19.7 -> 3.21.0"

cmake on darwin now depends on the SystemConfiguration framework.
Support for this has not yet been added to our bootstrapping.

We need to decide how to go further. As this is blocking staging-next
it is reverted.

This reverts commit 29bbaa1489.

pkgs/development/tools/build-managers/cmake/application-services.patch

@@ -1,8 +1,8 @@
 diff --git a/Source/CMakeLists.txt b/Source/CMakeLists.txt
-index 9a18184fd3..278d146dd1 100644
+index 1b6bb00d4c..487114daa8 100644
 --- a/Source/CMakeLists.txt
 +++ b/Source/CMakeLists.txt
-@@ -933,7 +933,6 @@ endif()
+@@ -893,7 +893,6 @@ endif()
  # On Apple we need CoreFoundation and CoreServices
  if(APPLE)
    target_link_libraries(CMakeLib "-framework CoreFoundation")
@@ -11,25 +11,27 @@ index 9a18184fd3..278d146dd1 100644
  
  if(WIN32 AND NOT UNIX)
 diff --git a/Source/cmGlobalXCodeGenerator.cxx b/Source/cmGlobalXCodeGenerator.cxx
-index 77403b076a..d5aac95e1e 100644
+index a5ce5d18f4..3d6838ce82 100644
 --- a/Source/cmGlobalXCodeGenerator.cxx
 +++ b/Source/cmGlobalXCodeGenerator.cxx
-@@ -49,10 +49,6 @@ struct cmLinkImplementation;
+@@ -43,11 +43,10 @@
+ 
+ struct cmLinkImplementation;
  
  #if !defined(CMAKE_BOOTSTRAP) && defined(__APPLE__)
- #  include <CoreFoundation/CoreFoundation.h>
--#  if !TARGET_OS_IPHONE
--#    define HAVE_APPLICATION_SERVICES
--#    include <ApplicationServices/ApplicationServices.h>
--#  endif
+-#  define HAVE_APPLICATION_SERVICES
+-#  include <ApplicationServices/ApplicationServices.h>
++#  include <CoreFoundation/CoreFoundation.h>
  #endif
- 
+
  #if !defined(CMAKE_BOOTSTRAP)
+ #  include "cmXMLParser.h"
+ 
 diff --git a/Utilities/cmlibarchive/CMakeLists.txt b/Utilities/cmlibarchive/CMakeLists.txt
-index 79452ffff6..a848731b7e 100644
+index bfcaf30bb7..1da540aee5 100644
 --- a/Utilities/cmlibarchive/CMakeLists.txt
 +++ b/Utilities/cmlibarchive/CMakeLists.txt
-@@ -2013,11 +2013,6 @@ IF(ENABLE_TEST)
+@@ -2007,11 +2007,6 @@ IF(ENABLE_TEST)
  ENDIF(ENABLE_TEST)
  ENDIF()
  

pkgs/development/tools/build-managers/cmake/default.nix

@@ -16,11 +16,12 @@ stdenv.mkDerivation rec {
           + lib.optionalString isBootstrap "-boot"
           + lib.optionalString useNcurses "-cursesUI"
           + lib.optionalString withQt5 "-qt5UI";
-  version = "3.21.0";
+  version = "3.19.7";
 
   src = fetchurl {
     url = "https://cmake.org/files/v${lib.versions.majorMinor version}/cmake-${version}.tar.gz";
-    sha256 = "sha256-SkLVZEmlH004CatNO2H9SpakaeViZuiWzhAJtXaL0qs=";
+    # compare with https://cmake.org/files/v${lib.versions.majorMinor version}/cmake-${version}-SHA-256.txt
+    sha256 = "sha256-WKFfDVagr8zDzFNxI0/Oc/zGyPnb13XYmOUQuDF1WI4=";
   };
 
   patches = [