sysconf: move in from cpp-cheat

arm baremetal: give more TTBR rationale

userland/posix/sysconf.c

@@ -0,0 +1,12 @@
+/* https://github.com/cirosantilli/linux-kernel-module-cheat#sysconf */
+
+#define _XOPEN_SOURCE 700
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+
+int main(void) {
+    /* Maximum lengh of command line arguments + environment variables: */
+    printf("_SC_ARG_MAX (MiB) = %ld\n", sysconf(_SC_ARG_MAX) / (1 << 20));
+    return EXIT_SUCCESS;
+}