update cmake target to 3.31.6, remove invalid specifier

see: https://cmake.org/cmake/help/latest/command/add_custom_command.html

Author: mazunki

lib/LiveUpdate/CMakeLists.txt

@@ -1,4 +1,4 @@
-cmake_minimum_required(VERSION 3.6.0)
+cmake_minimum_required(VERSION 3.31.6)
 
 set(CMAKE_TRY_COMPILE_TARGET_TYPE STATIC_LIBRARY)
 
@@ -29,7 +29,6 @@ set(CMAKE_CXX_COMPILER_TARGET ${TRIPLE})
 set(CMAKE_C_COMPILER_TARGET ${TRIPLE})
 
 add_custom_command(
-  PRE_BUILD
   OUTPUT ${CMAKE_CURRENT_BINARY_DIR}/hotswap64.bin
 	COMMAND ${CMAKE_ASM_NASM_COMPILER} -f bin -o ${CMAKE_CURRENT_BINARY_DIR}/hotswap64.bin ${CMAKE_CURRENT_SOURCE_DIR}/src/hotswap64.asm
   COMMENT "Building hotswap binary"

test/CMakeLists.txt

@@ -1,4 +1,4 @@
-cmake_minimum_required(VERSION 3.6.0)
+cmake_minimum_required(VERSION 3.31.6)
 
 project(unittests C CXX)
 set(CMAKE_CXX_STANDARD 20)
@@ -250,7 +250,6 @@ add_custom_command(TARGET clangtidy
 
 if (GENERATE_SUPPORT_FILES)
   add_custom_command( OUTPUT ${CMAKE_CURRENT_BINARY_DIR}/test-tar-gz-inside.tar
-    PRE_BUILD
     COMMAND ${CMAKE_COMMAND} -E tar cf ${CMAKE_CURRENT_BINARY_DIR}/test-single.tar ${CMAKE_CURRENT_SOURCE_DIR}/CMakeLists.txt
     COMMAND ${CMAKE_COMMAND} -E tar cf ${CMAKE_CURRENT_BINARY_DIR}/test-multiple.tar ${CMAKE_CURRENT_SOURCE_DIR}/*.py
     COMMAND ${CMAKE_COMMAND} -E copy ${CMAKE_CURRENT_SOURCE_DIR}/CMakeLists.txt ${CMAKE_CURRENT_BINARY_DIR}/test-invalid.tar