rewrite systemconfig in C and link statically

systemconfig (a.k.a "activate") is run from the initramfs. Converting
it from a shell script to an executable means it doesn't depend on
there being a shell in the initramfs

pkgs/systemconfig/defs.h

@@ -0,0 +1,37 @@
+#include <sys/stat.h>
+#include <unistd.h>
+#include <sys/sysmacros.h>
+#include <fcntl.h>
+#include <string.h>
+#include <stdlib.h>
+
+void print_file(char * path, mode_t mode, char * text) {
+  int fd = open(path, O_CREAT | O_WRONLY, mode);
+  char *p, *nxt;
+  char b[1];
+  if(fd >=0) {
+    p = text;
+    while(nxt = strchr(p, '\\')) {
+      char upper = nxt[2];
+      char lower = nxt[3];
+      upper = (upper>'9') ? ((upper | 32) - 'a' + 10) : (upper - '0');
+      lower = (lower>'9') ? ((lower | 32) - 'a' + 10) : (lower - '0');
+      b[0] = (upper << 4) + lower;
+      write(fd, p, nxt-p);
+      write(fd, b, 1);
+      p=nxt+4;
+    }
+    write(fd, p, strlen(p));
+    close(fd);
+  }
+}
+
+
+
+#define PRINTFILE(path, mode, text) print_file(path, (mode_t) mode, text)
+#define MKDIR(path, mode) mkdir(path, mode)
+#define MKNOD_C(path, mode, major,minor) mknod(path, mode | S_IFCHR, makedev(major, minor))
+#define MKNOD_B(path, mode, major,minor) mknod(path, mode | S_IFBLK, makedev(major, minor))
+#define LN_S(target, path) (void)symlink(target, path)
+#define LN(target, path) link(target, path)
+#define MKNOD_P(path, mode) mkfifo(path, mode)