kbuild: add LEX and YACC variables

Allow users to use their favorite lexer / parser generators.
This is useful for me to test various flex and bison versions.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

Makefile

@@ -377,6 +377,8 @@ NM		= $(CROSS_COMPILE)nm
 STRIP		= $(CROSS_COMPILE)strip
 OBJCOPY		= $(CROSS_COMPILE)objcopy
 OBJDUMP		= $(CROSS_COMPILE)objdump
+LEX		= flex
+YACC		= bison
 AWK		= awk
 GENKSYMS	= scripts/genksyms/genksyms
 INSTALLKERNEL  := installkernel
@@ -428,7 +430,7 @@ GCC_PLUGINS_CFLAGS :=
 
 export ARCH SRCARCH CONFIG_SHELL HOSTCC HOSTCFLAGS CROSS_COMPILE AS LD CC
 export CPP AR NM STRIP OBJCOPY OBJDUMP HOSTLDFLAGS HOST_LOADLIBES
-export MAKE AWK GENKSYMS INSTALLKERNEL PERL PYTHON UTS_MACHINE
+export MAKE LEX YACC AWK GENKSYMS INSTALLKERNEL PERL PYTHON UTS_MACHINE
 export HOSTCXX HOSTCXXFLAGS LDFLAGS_MODULE CHECK CHECKFLAGS
 
 export KBUILD_CPPFLAGS NOSTDINC_FLAGS LINUXINCLUDE OBJCOPYFLAGS LDFLAGS

scripts/Makefile.lib

@@ -193,7 +193,7 @@ ifdef REGENERATE_PARSERS
 LEX_PREFIX = $(if $(LEX_PREFIX_${baseprereq}),$(LEX_PREFIX_${baseprereq}),yy)
 
 quiet_cmd_flex = LEX     $@
-      cmd_flex = flex -o$@ -L -P $(LEX_PREFIX) $<
+      cmd_flex = $(LEX) -o$@ -L -P $(LEX_PREFIX) $<
 
 .PRECIOUS: $(src)/%.lex.c_shipped
 $(src)/%.lex.c_shipped: $(src)/%.l
@@ -204,7 +204,7 @@ $(src)/%.lex.c_shipped: $(src)/%.l
 YACC_PREFIX = $(if $(YACC_PREFIX_${baseprereq}),$(YACC_PREFIX_${baseprereq}),yy)
 
 quiet_cmd_bison = YACC    $@
-      cmd_bison = bison -o$@ -t -l -p $(YACC_PREFIX) $<
+      cmd_bison = $(YACC) -o$@ -t -l -p $(YACC_PREFIX) $<
 
 .PRECIOUS: $(src)/%.tab.c_shipped
 $(src)/%.tab.c_shipped: $(src)/%.y