Kbuild: enable toolchain newlib library instead of minimal libc

This options allows us to link against newlib instead of the
integrated minimal c library.

Change-Id: I20990354d74c08f2f6348f0aeea452b8f0f4c8e9
Signed-off-by: Anas Nashif <anas.nashif@intel.com>

lib/libc/newlib/libc-hooks.c

@@ -0,0 +1,105 @@
+#include <errno.h>
+#include <stdio.h>
+#include <sys/stat.h>
+
+#define HEAP_SIZE 4096
+unsigned char heap[HEAP_SIZE];
+unsigned int heap_sz = 0;
+
+static int _stdout_hook_default(int c) {
+        (void)(c);  /* Prevent warning about unused argument */
+
+        return EOF;
+}
+
+static int (*_stdout_hook)(int) = _stdout_hook_default;
+
+void __stdout_hook_install(int (*hook)(int)) {
+        _stdout_hook = hook;
+}
+
+static unsigned char _stdin_hook_default(void) {
+        return 0;
+}
+
+static unsigned char (*_stdin_hook)(void) = _stdin_hook_default;
+
+void __stdin_hook_install(unsigned char (*hook)(void)) {
+        _stdin_hook = hook;
+}
+
+int read( int fd, char *buf, int nbytes) {
+	int i = 0;
+
+	for (i = 0; i < nbytes; i++) {
+		*(buf + i) = _stdin_hook();
+		if ((*(buf + i) == '\n') || (*(buf + i) == '\r')) {
+			i++;
+			break;
+		}
+	}
+	return (i);
+}
+
+int write(int fd, char *buf, int nbytes) {
+	int i;
+
+	for (i = 0; i < nbytes; i++) {
+		if (*(buf + i) == '\n') {
+			_stdout_hook ('\r');
+		}
+		_stdout_hook (*(buf + i));
+	}
+	return (nbytes);
+}
+
+int fstat( int fd, struct stat *buf) {
+	buf->st_mode = S_IFCHR;       /* Always pretend to be a tty */
+	buf->st_blksize = 0;
+
+	return (0);
+}
+
+int isatty(int file) {
+	return 1;
+}
+
+
+int kill(int i, int j) {
+	return 0;
+}
+
+int getpid() {
+	return 0;
+}
+
+int _fstat(int file, struct stat *st) {
+	st->st_mode = S_IFCHR;
+	return 0;
+}
+
+
+void exit(int status) {
+	write(1, "exit", 4);
+	while (1) {
+		;
+	}
+}
+
+int close(int file) {
+	return -1;
+}
+
+int lseek(int file, int ptr, int dir) {
+	return 0;
+}
+
+void *sbrk(int count) {
+	void *ptr = heap + heap_sz;
+	if ((heap_sz + count) <= HEAP_SIZE) {
+		heap_sz += count;
+		return ptr;
+	} else {
+		return (void *)-1;
+	}
+}