fix flex problem

src/CMakeLists.txt

@@ -1,10 +1,10 @@
 find_package(FLEX REQUIRED)
-execute_process(COMMAND flex scan.l WORKING_DIRECTORY src)
+flex_target(scan src/scan.l src/lex.yy.c COMPILE_FLAGS --header-file="src/lex.yy.h")
 
 add_library(picrin SHARED
   src/blob.c src/bool.c src/char.c src/codegen.c src/cont.c src/error.c
-  src/file.c src/gc.c src/init.c src/lex.yy.c src/lib.c src/load.c src/macro.c
+  src/file.c src/gc.c src/init.c src/lib.c src/load.c src/macro.c
   src/number.c src/pair.c src/port.c src/proc.c src/read.c src/state.c
   src/string.c src/symbol.c src/system.c src/time.c src/var.c src/vector.c
-  src/vm.c src/write.c)
+  src/vm.c src/write.c ${PROJECT_SOURCE_DIR}/src/lex.yy.c)
 target_link_libraries(picrin m xfile)

src/scan.l

@@ -29,7 +29,6 @@
 %option noyywrap
 
 %option extra-type="struct parser_control *"
-%option header-file="lex.yy.h"
 %option never-interactive
 
   /* comment */