Move flex and bison package finding to the main root and check the ve…

…rsion of flex for the --header-file, really this is XHP which has this requirement

CMake/HPHPFindLibs.cmake

@@ -157,13 +157,19 @@ FIND_LIBRARY (BINUTIL_LIB iberty)
 FIND_LIBRARY (DL_LIB dl)
 
 if (BFD_LIB STREQUAL "BFD_LIB-NOTFOUND")
-  message(FATAL_ERROR "You need to install binutils")
+	message(FATAL_ERROR "You need to install binutils")
 endif()
 
 if (BINUTIL_LIB STREQUAL "BINUTIL_LIB-NOTFOUND")
-  message(FATAL_ERROR "You need to install binutils")
+	message(FATAL_ERROR "You need to install binutils")
 endif()
 
+find_package(BISON REQUIRED)
+find_package(FLEX REQUIRED)
+
+if (${FLEX_VERSION} VERSION_LESS 2.5.33)
+	message(FATAL_ERROR "Flex is too old, found ${FLEX_VERSION} and we need 2.5.33")
+endif()
 
 include_directories(${HPHP_HOME}/src)
 include_directories(${HPHP_HOME}/src/lib/system/gen)

src/CMakeLists.txt

@@ -73,9 +73,6 @@ endforeach(t ${HPHP_EXCLUDE_FILES})
 
 #list(REMOVE_ITEM CXX_SOURCES "${CXX_NOOPT_SOURCES}")
 
-find_package(BISON REQUIRED)
-find_package(FLEX REQUIRED)
-
 FLEX_TARGET(HphpScanner ${CMAKE_CURRENT_SOURCE_DIR}/cpp/eval/parser/hphp.x ${CMAKE_CURRENT_SOURCE_DIR}/cpp/eval/parser/lex.eval_.cpp COMPILE_FLAGS " -w -i -Peval_")
 BISON_TARGET(HphpParser ${CMAKE_CURRENT_SOURCE_DIR}/cpp/eval/parser/hphp.y ${CMAKE_CURRENT_SOURCE_DIR}/cpp/eval/parser/hphp.tab.cpp  COMPILE_FLAGS " -v -d -p eval_")
 ADD_FLEX_BISON_DEPENDENCY(HphpScanner HphpParser)