Regenerate CMake files list from upmake too

Replace the specialized Python script used for it before (and which was
actually forgotten to run a couple of times already) with a newer
version of upmake, which can now update CMake variable definitions too.

build/upmake_script.pl

@@ -10,6 +10,7 @@ use FindBin qw($Bin);
 
 use Makefile::Update;
 use Makefile::Update::Bakefile0;
+use Makefile::Update::CMakefile;
 use Makefile::Update::MSBuild;
 use Makefile::Update::VCProj;
 
@@ -57,6 +58,10 @@ if (!$only_msvs) {
     }
 }
 
+if (!$only_msvs && !$only_bkl) {
+    call_upmake("$Bin/cmake/files.cmake", \&update_cmakefile, $vars);
+}
+
 if (!$only_bkl) {
     # Path to the project root directory from the directory containing the
     # projects.