gem5: update to 7bfb7f3a43f382eb49853f47b140bfd6caad0fb8

The update is required to include 3c3ca64b5f0dd9eef7b1ce1c65cc6e8e9147dd38
otherwise baremetal does not on VExpress.

baremetal: create a baremetal setup with crosstool-ng

buildroot: improve directory location: move out/dl inside
out/buildroot/download, and add a new out/buildroot/build level

tagline: generalize, deliver more value than howto, since now howtos
are starting to multiply

rename all top scripts to separate words with hyphen more consistently,
e.g. run-gdb instead of rungdb

getvar: list all variables

gem5: make m5out section to focus all releated information at

Prevent m5term Text file busy when rebuilding gem5 while it is running.

baremetal/prompt.c

@@ -0,0 +1,22 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+void main(void) {
+    char c;
+    char *ptr = NULL;
+    size_t alloc_size = 1;
+    while (1) {
+        printf("enter a character\n");
+        c = getchar();
+        printf("got: %c\n", c);
+        ptr = realloc(ptr, alloc_size);
+        if (ptr == NULL) {
+            puts("out of memory");
+            break;
+        } else {
+            printf("new alloc of %d bytes at address 0x%p\n", alloc_size, ptr);
+            alloc_size <<= 1;
+        }
+    }
+}
+