Use fl LIBS instead of :libfl.a

Rsconscript

@@ -2,7 +2,6 @@ configure do
   check_cxx_compiler
   check_program "flex"
   check_program "bison"
-  check_lib ":libfl.a"
   check_lib "pthread"
   check_lib "freeimage"
 end
@@ -10,6 +9,7 @@ end
 env do |env|
   env["CCFLAGS"] += %w[-Wall -O2]
   env["CPPPATH"] += glob("src/**")
+  env["LIBS"] += %w[fl]
 
   env.CFile("^/parser/lexer.cc", "src/parser/parser.ll")
   env.CFile("^/parser/parser.cc", "src/parser/parser.yy")