kconfig: get CONFIG_ prefix from the environment

Currently, the CONFIG_ prefix is hard-coded in the kconfig frontends
executables. This means that two projects that use kconfig with
different prefixes can not share the same kconfig frontends.

Instead of hard-coding the prefix in the frontends, get it from the
environment, and revert back to hard-coded value if not found.
Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Signed-off-by: Michal Marek <mmarek@suse.cz>

scripts/kconfig/gconf.c

@@ -10,6 +10,7 @@
 #  include <config.h>
 #endif
 
+#include <stdlib.h>
 #include "lkc.h"
 #include "images.c"
 
@@ -22,7 +23,6 @@
 #include <string.h>
 #include <unistd.h>
 #include <time.h>
-#include <stdlib.h>
 
 //#define DEBUG
 

scripts/kconfig/lkc.h

@@ -41,7 +41,7 @@ extern "C" {
 #endif
 static inline const char *CONFIG_prefix(void)
 {
-	return CONFIG_;
+	return getenv( "CONFIG_" ) ?: CONFIG_;
 }
 #undef CONFIG_
 #define CONFIG_ CONFIG_prefix()

scripts/kconfig/nconf.c

@@ -7,6 +7,7 @@
  */
 #define _GNU_SOURCE
 #include <string.h>
+#include <stdlib.h>
 
 #include "lkc.h"
 #include "nconf.h"