Tests: Simplify CTest.BuildCommand.ProjectInSubdir configuration

Collect all ctest_configure options in a list to configure it into the
test script.  Drop the unused -DCMAKE_MAKE_PROGRAM argument to ctest.

Tests/CMakeLists.txt

@@ -1829,17 +1829,18 @@ ${CMake_BINARY_DIR}/bin/cmake -DVERSION=master -P ${CMake_SOURCE_DIR}/Utilities/
 #        )
 
   # A test for ctest_build() with targets in subdirectories
+  set(ctest_configure_options)
   if(CMAKE_TEST_GENERATOR_TOOLSET)
-    set(CMAKE_TEST_GENERATOR_TOOLSET_SELECTION "-T;${CMAKE_TEST_GENERATOR_TOOLSET};")
-  else()
-    set(CMAKE_TEST_GENERATOR_TOOLSET_SELECTION)
+    list(APPEND ctest_configure_options -T ${CMAKE_TEST_GENERATOR_TOOLSET})
+  endif()
+  if(CMAKE_TEST_MAKEPROGRAM)
+    list(APPEND ctest_configure_options -DCMAKE_MAKE_PROGRAM:FILEPATH=${CMAKE_TEST_MAKEPROGRAM})
   endif()
   configure_file("${CMake_SOURCE_DIR}/Tests/CTestBuildCommandProjectInSubdir/CTestBuildCommandProjectInSubdir.cmake.in"
                  "${CMake_BINARY_DIR}/Tests/CTestBuildCommandProjectInSubdir/CTestBuildCommandProjectInSubdir.cmake" @ONLY)
-  unset(CMAKE_TEST_GENERATOR_TOOLSET_SELECTION)
+  unset(ctest_configure_options)
   add_test(CTest.BuildCommand.ProjectInSubdir
-    ${CMAKE_CTEST_COMMAND} -S "${CMake_BINARY_DIR}/Tests/CTestBuildCommandProjectInSubdir/CTestBuildCommandProjectInSubdir.cmake"
-                           -DCMAKE_MAKE_PROGRAM:FILEPATH=${CMAKE_TEST_MAKEPROGRAM})
+    ${CMAKE_CTEST_COMMAND} -S "${CMake_BINARY_DIR}/Tests/CTestBuildCommandProjectInSubdir/CTestBuildCommandProjectInSubdir.cmake")
   list(APPEND TEST_BUILD_DIRS "${CMake_BINARY_DIR}/Tests/CTestBuildCommandProjectInSubdir/Nested")
 
   set(CTEST_TEST_UPDATE 1)

Tests/CTestBuildCommandProjectInSubdir/CTestBuildCommandProjectInSubdir.cmake.in

@@ -8,5 +8,5 @@ set(CTEST_BUILD_CONFIGURATION "@CTestTest_CONFIG@")
 
 ctest_empty_binary_directory(${CTEST_BINARY_DIRECTORY})
 ctest_start(Experimental)
-ctest_configure(OPTIONS "@CMAKE_TEST_GENERATOR_TOOLSET_SELECTION@-DCMAKE_MAKE_PROGRAM:FILEPATH=@CMAKE_TEST_MAKEPROGRAM@")
+ctest_configure(OPTIONS "@ctest_configure_options@")
 ctest_build(TARGET test)