support/testing: test_iso9660: bump to kernel 4.19.204

The kernel 4.11 curently used by the test doesn't build with host
gcc >= 10 due the gcc default -fno-common. See GCC 10 porting guide [1].

/usr/bin/ld: scripts/dtc/dtc-parser.tab.o:(.bss+0x20): multiple definition of `yylloc'; scripts/dtc/dtc-lexer.lex.o:(.bss+0x0): first defined here

Update to the latest 4.19 LTS version but doing so requires to
disable CONFIG_RETPOLINE since the toolchain is not retpoline
capable [2].

Fixes:
https://gitlab.com/kubu93/buildroot/-/jobs/1564202078

[1] https://gcc.gnu.org/gcc-10/porting_to.html
[2] https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=8c4ad5d39144776c2987e81609204e1766ed4190

Signed-off-by: Romain Naour <romain.naour@gmail.com>
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
(cherry picked from commit 23a8baa779825554105c6b002d4acbe4e9bbe340)
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

support/testing/conf/minimal-x86-qemu-kernel.config

@@ -2,6 +2,7 @@ CONFIG_SYSVIPC=y
 CONFIG_MODULES=y
 CONFIG_MODULE_UNLOAD=y
 CONFIG_SMP=y
+# CONFIG_RETPOLINE is not set
 CONFIG_HYPERVISOR_GUEST=y
 CONFIG_PARAVIRT=y
 CONFIG_NET=y

support/testing/tests/fs/test_iso9660.py

@@ -18,7 +18,7 @@ BASIC_CONFIG = \
     BR2_TARGET_GENERIC_GETTY_BAUDRATE_115200=y
     BR2_LINUX_KERNEL=y
     BR2_LINUX_KERNEL_CUSTOM_VERSION=y
-    BR2_LINUX_KERNEL_CUSTOM_VERSION_VALUE="4.11"
+    BR2_LINUX_KERNEL_CUSTOM_VERSION_VALUE="4.19.204"
     BR2_LINUX_KERNEL_USE_CUSTOM_CONFIG=y
     BR2_LINUX_KERNEL_CUSTOM_CONFIG_FILE="{}"
     # BR2_TARGET_ROOTFS_TAR is not set