gkermit: Fix compilation with -Wimplicit-function-declaration

Cleaned up Makefile for consistency between packages.

Signed-off-by: Rosen Penev <rosenp@gmail.com>

utils/gkermit/patches/010-musl.patch

@@ -0,0 +1,29 @@
+--- a/gcmdline.c
++++ b/gcmdline.c
+@@ -29,6 +29,7 @@
+ */
+ 
+ #include <stdio.h>
++#include <stdlib.h>
+ #include "gkermit.h"
+ 
+ /* Externals */
+@@ -53,7 +54,7 @@ _MYPROTOTYPE( VOID fatal, (char *) );
+ _MYPROTOTYPE( VOID usage, (void) );
+ 
+ #ifndef NOGETENV
+-_MYPROTOTYPE( char * getenv, (char *) );
++_MYPROTOTYPE( char * getenv, (const char *) );
+ #define GARGC 32
+ #define GBUFSIZ 256
+ static char gbuf[GBUFSIZ], *gargs[GARGC], *gptr = NULL;
+--- a/gunixio.c
++++ b/gunixio.c
+@@ -58,6 +58,7 @@
+ */
+ 
+ #include <stdio.h>			/* Standard input/output */
++#include <stdlib.h>
+ 
+ #ifdef POSIX
+ #include <termios.h>			/* Terminal modes */