configure: Add --with-gperf option

On OS X, Apple supply an old gperf (3.0.3) with xcode and
xcode commandline tools which causes build failures:

./zconf.hash.c:183:17: error: expected expression
{offsetof(struct kconf_id_strings_t, kconf_id_strings_str2),

.. upgrading to gperf 3.0.4 was sufficient to fix this,
so this option allows the user to specify the gperf
program that they wish to use.

To install gperf 3.0.4 from homebrew, I did:

    brew tap homebrew/dupes
    brew install homebrew/dupes/gperf

.. then passed --with-gperf=$BREWFIX/Cellar/gperf/3.0.4/bin/gperf
to configure

Signed-off-by: Ray Donnelly <mingw.android@gmail.com>
Message-Id: <CAOYw7dtCmcJ9WiqmQ81MmZeRPcV-tDOqe9=kRDW4uQGuZNd2Ng@mail.gmail.com>
Patchwork-Id: 274892

Makefile.in

@@ -68,6 +68,7 @@ export objcopy         := @OBJCOPY@
 export objdump         := @OBJDUMP@
 export readelf         := @READELF@
 export patch           := @PATCH@
+export gperf           := @GPERF@
 export CC              := @CC@
 export CPP             := @CPP@
 export CPPFLAGS        := @CPPFLAGS@
@@ -212,6 +213,7 @@ paths.mk: FORCE
 	  echo 'export objdump=$(objdump)';         \
 	  echo 'export readelf=$(readelf)';         \
 	  echo 'export patch=$(patch)';             \
+	  echo 'export gperf=$(gperf)';             \
 	 ) >$@
 
 paths.sh: FORCE
@@ -228,6 +230,7 @@ paths.sh: FORCE
 	  echo 'export objdump="$(objdump)"';       \
 	  echo 'export readelf="$(readelf)"';       \
 	  echo 'export patch="$(patch)"';           \
+	  echo 'export gperf="$(gperf)"';           \
 	 ) >$@
 
 config/configure.in: FORCE

configure.ac

@@ -143,15 +143,19 @@ AC_ARG_WITH([readelf],
     AS_HELP_STRING([--with-readelf=PATH],
                    [Specify the full PATH to GNU readelf]),
     [READELF=$withval])
+AC_ARG_WITH([gperf],
+    AS_HELP_STRING([--with-gperf=PATH],
+                   [Specify the full PATH to GNU gperf]),
+    [GPERF=$withval])
 
 AC_PROG_RANLIB
 ACX_PATH_TOOL_REQ([OBJCOPY], [objcopy])
 ACX_PATH_TOOL_REQ([OBJDUMP], [objdump])
 ACX_PATH_TOOL_REQ([READELF], [readelf])
+ACX_PATH_TOOL_REQ([GPERF], [gperf])
 
 ACX_CHECK_PROGS_REQ([bison], [bison])
 ACX_CHECK_PROGS_REQ([flex], [flex])
-ACX_CHECK_PROGS_REQ([gperf], [gperf])
 ACX_CHECK_PROGS_REQ([makeinfo], [makeinfo])
 ACX_CHECK_PROGS_REQ([cut], [cut])
 ACX_CHECK_PROGS_REQ([stat], [stat])

kconfig/Makefile

@@ -84,7 +84,7 @@ zconf.tab.c: zconf.y
 
 zconf.hash.c: zconf.gperf
 	@echo "  GPERF  '$@'"
-	@gperf < $< > $@
+	@$(gperf) < $< > $@
 
 lex.zconf.c: zconf.l
 	@echo "  LEX    '$@'"