Build process requires additional `make opensbi-rebuild`

[bluewww]

After setting up buildroot with make setup and building it through make -j we have to issue an additional make opensbi-rebuild to get a working image. If the last step is not done booting will be stuck at

[    0.023012] printk: legacy console [tty0] enabled
[    0.029445] printk: legacy bootconsole [sbi0] disabled

This is the result of diffing a good and bad image

--- fw_payload_bad.dump 2024-05-24 16:26:22.248431363 +0200
+++ fw_payload_good.dump        2024-05-24 16:26:07.450118694 +0200
@@ -1,5 +1,5 @@

-output/images-corrupted/fw_payload.elf:     file format elf64-littleriscv
+output/images/fw_payload.elf:     file format elf64-littleriscv


Disassembly of section .text:
@@ -3590,7 +3590,7 @@
    800027a4:  357d                    addiw   a0,a0,-1
    800027a6:  fffc17b7                lui     a5,0xfffc1
    800027aa:  03f57513                andi    a0,a0,63
-    800027ae:  17fd                    addi    a5,a5,-1 # fffffffffffc0fff <_fw_reloc_end+0xffffffff7f121387>
+    800027ae:  17fd                    addi    a5,a5,-1 # fffffffffffc0fff <_fw_reloc_end+0xffffffff7ed21387>
    800027b0:  0532                    slli    a0,a0,0xc
    800027b2:  8cfd                    and     s1,s1,a5
    800027b4:  8cc9                    or      s1,s1,a0
@@ -5883,7 +5883,7 @@
    80003e28:  105026f3                csrr    a3,stvec
    80003e2c:  1084b783                ld      a5,264(s1)
    80003e30:  7779                    lui     a4,0xffffe
-    80003e32:  6ff70713                addi    a4,a4,1791 # ffffffffffffe6ff <_fw_reloc_end+0xffffffff7f15ea87>
+    80003e32:  6ff70713                addi    a4,a4,1791 # ffffffffffffe6ff <_fw_reloc_end+0xffffffff7ed5ea87>
    80003e36:  10d4b023                sd      a3,256(s1)
    80003e3a:  4685                    li      a3,1
    80003e3c:  8ff9                    and     a5,a5,a4
    
    [...]