Update CMakeLists.txt

CMakeLists.txt

@@ -5,14 +5,19 @@ project(pocketpy)
 set(CMAKE_CXX_STANDARD 17)
 set(CMAKE_CXX_STANDARD_REQUIRED ON)
 
+find_program(PYTHON3 python)
+if(NOT PYTHON3)
+    find_program(PYTHON3 python3)
+endif()
+
 execute_process(
-    COMMAND python prebuild.py
+    COMMAND ${PYTHON3} prebuild.py
     WORKING_DIRECTORY ${CMAKE_CURRENT_LIST_DIR}
     RESULT_VARIABLE PREBUILD_RESULT
 )
 
 if(NOT ${PREBUILD_RESULT} EQUAL 0)
-    message(FATAL_ERROR "Prebuild failed with code ${PREBUILD_RESULT}")
+    message(FATAL_ERROR "prebuild.py: ${PREBUILD_RESULT}")
 endif()
 
 if(MSVC)
@@ -32,14 +37,10 @@ include_directories(${CMAKE_CURRENT_LIST_DIR}/include)
 
 aux_source_directory(${CMAKE_CURRENT_LIST_DIR}/src POCKETPY_SRC)
 
-if(NOT PK_BUILD_EXE AND NOT PK_BUILD_SHARED_LIB AND NOT PK_BUILD_STATIC_LIB)
-    set(PK_BUILD_EXE ON)
-endif()
-
-if(PK_BUILD_EXE)
-    add_executable(${PROJECT_NAME} ${POCKETPY_SRC} src2/main.cpp)
-elseif(PK_BUILD_SHARED_LIB)
+if(PK_BUILD_SHARED_LIB)
     add_library(${PROJECT_NAME} SHARED ${POCKETPY_SRC} src2/lib.cpp)
 elseif(PK_BUILD_STATIC_LIB)
     add_library(${PROJECT_NAME} STATIC ${POCKETPY_SRC} src2/lib.cpp)
+else()
+    add_executable(${PROJECT_NAME} ${POCKETPY_SRC} src2/main.cpp)
 endif()