baremetal: build userland/ programs using baremetal path property instead of symlinks

Otherwise I'll go crazy with symlink action.

userland/c/assert_fail.c

@@ -1 +0,0 @@
-../../lkmc/c/assert_fail.c

userland/c/assert_fail.c

@@ -0,0 +1,18 @@
+/* Let's see what happens when an assert fails.
+ *
+ * Outcome on Ubuntu 19.04 shows the failure line:
+ *
+ *     assert_fail.out: /path/to/linux-kernel-module-cheat/userland/c/assert_fail.c:15: main: Assertion `0' failed.
+ *
+ * and exit status 134 == 128 + 6, which corresponds to SIGABORT (6).
+ */
+
+#include <assert.h>
+#include <stdlib.h>
+#include <stdio.h>
+
+int main(void) {
+    assert(0);
+    puts("here");
+    return EXIT_SUCCESS;
+}