Move the distclean definition to add_custom_target

Normally this should not be provided since most builds in CMake land are out-of-source and if provided it should be by CMake to account for specific generator files

Author: LecrisUT

zproject_cmake.gsl

@@ -602,34 +602,33 @@ include(CTest)
 # cleanup
 ########################################################################
 if (NOT TARGET distclean)
-    add_custom_target (distclean @echo Cleaning for source distribution)
+    if (CMAKE_VERSION VERSION_LESS 3.17)
+        set(rm_command rm -rf)
+    else()
+        set(rm_command ${CMAKE_COMMAND} -E rm -rf --)
+    endif()
+    set(cmake_generated ${PROJECT_BINARY_DIR}/CMakeCache.txt
+                        ${PROJECT_BINARY_DIR}/cmake_install.cmake
+                        ${PROJECT_BINARY_DIR}/Makefile
+                        ${PROJECT_BINARY_DIR}/CMakeFiles
+                        ${PROJECT_BINARY_DIR}/CTestTestfile.cmake
+                        ${PROJECT_BINARY_DIR}/DartConfiguration.tcl
+                        ${PROJECT_BINARY_DIR}/Testing
+                        ${PROJECT_BINARY_DIR}/compile_commands.json
+                        ${PROJECT_BINARY_DIR}/platform.h
+                        ${PROJECT_BINARY_DIR}/src/$(project.libname).pc
+                        ${PROJECT_BINARY_DIR}/src/$(project.libname).so
+                        ${PROJECT_BINARY_DIR}/src/$(project.name)_selftest
+    .for project.main
+                        ${PROJECT_BINARY_DIR}/src/$(main.name)
+    .endfor
+    )
+    add_custom_target(distclean
+        COMMAND ${rm_command} CMakeTmp ${cmake_generated}
+        COMMENT Cleaning for source distribution
+    )
 endif()
 
-set(cmake_generated ${PROJECT_BINARY_DIR}/CMakeCache.txt
-                    ${PROJECT_BINARY_DIR}/cmake_install.cmake
-                    ${PROJECT_BINARY_DIR}/Makefile
-                    ${PROJECT_BINARY_DIR}/CMakeFiles
-                    ${PROJECT_BINARY_DIR}/CTestTestfile.cmake
-                    ${PROJECT_BINARY_DIR}/DartConfiguration.tcl
-                    ${PROJECT_BINARY_DIR}/Testing
-                    ${PROJECT_BINARY_DIR}/compile_commands.json
-                    ${PROJECT_BINARY_DIR}/platform.h
-                    ${PROJECT_BINARY_DIR}/src/$(project.libname).pc
-                    ${PROJECT_BINARY_DIR}/src/$(project.libname).so
-                    ${PROJECT_BINARY_DIR}/src/$(project.name)_selftest
-.for project.main
-                    ${PROJECT_BINARY_DIR}/src/$(main.name)
-.endfor
-)
-
-add_custom_command(
-    DEPENDS clean
-    COMMENT "distribution clean"
-    COMMAND rm
-    ARGS    -rf CMakeTmp ${cmake_generated}
-    TARGET  distclean
-)
-
 include(ClangFormat OPTIONAL)
 
 ########################################################################