Tests: Fix CMAKE_MAKE_PROGRAM selection in CMakeOnly tests

Use the explicitly-tested make program, if any.

Tests/CMakeOnly/Test.cmake.in

@@ -2,6 +2,11 @@ if (NOT TEST_SOURCE)
   set(TEST_SOURCE "${TEST}")
 endif ()
 
+set(make_program "@CMake_TEST_EXPLICIT_MAKE_PROGRAM@")
+if(make_program)
+  set(maybe_make_program "-DCMAKE_MAKE_PROGRAM=${make_program}")
+endif()
+
 set(source_dir "@CMAKE_CURRENT_SOURCE_DIR@/${TEST_SOURCE}")
 set(binary_dir "@CMAKE_CURRENT_BINARY_DIR@/${TEST}-build")
 file(REMOVE_RECURSE "${binary_dir}")
@@ -11,6 +16,7 @@ execute_process(
   "${source_dir}" -G "@CMAKE_GENERATOR@"
   -A "@CMAKE_GENERATOR_PLATFORM@"
   -T "@CMAKE_GENERATOR_TOOLSET@"
+  ${maybe_make_program}
   WORKING_DIRECTORY "${binary_dir}"
   RESULT_VARIABLE result
   )