lava: add fastboot_fastrpc template for correct firmware archive merge

Introduce templates/boot/fastboot_fastrpc.jinja2 for FastRPC LAVA jobs.

FastRPC jobs provide firmware in archives. Combining kernel firmware and fastrpc
firmware archives with `cat` does not merge filesystem structures and can break
symlink/path resolution during early boot (e.g., /lib -> /usr/lib with firmware
delivered in a separate archive). This leads to firmware load failures.

The new template performs an extract-into-one-dir + repack workflow to produce a
single unified firmware archive while preserving directory layout and symlinks.

This is an additive change and does not modify the existing
templates/boot/fastboot.jinja2 behavior.

Signed-off-by: Tharun Kumar Merugu <mtharu@qti.qualcomm.com>

Author: quic-mtharu

templates/boot/fastboot_fastrpc.jinja2

@@ -0,0 +1,62 @@
+- deploy:
+    images:
+      image:
+        url: '{{ node.artifacts.kernel }}'
+      dtb:
+        url: '{{ node.artifacts.dtb }}'
+      {% if node.artifacts.firmware %}
+      ramdisk_firmware:
+        url: '{{ node.artifacts.firmware }}'
+      {% endif %}
+      ramdisk:
+        url: '{{ node.artifacts.ramdisk }}'
+        compression: gz
+        format: cpio.newc
+        overlays:
+          lava: true
+{% filter indent(width=10) %}
+{% block testoverlays %}{% endblock %}
+{% endfilter %}
+{% set dtb_path = node.artifacts.dtb.split('?')[0] %}
+{% set dtb_name = dtb_path.split('/')[-1] %}
+{% if node.artifacts.firmware %}
+{% set firmware_path = node.artifacts.firmware.split('?')[0] %}
+{% set firmware_name = firmware_path.split('/')[-1] %}
+{% endif %}
+{% set ramdisk_path = node.artifacts.ramdisk.split('?')[0] %}
+{% set ramdisk_name = ramdisk_path.split('/')[-1] %}
+    postprocess:
+      docker:
+        image: ghcr.io/mwasilew/docker-mkbootimage:master
+        steps:
+        - rm -rf rootfs
+        - mkdir rootfs
+        - cd rootfs
+        - apt-get update -q && DEBIAN_FRONTEND=noninteractive apt-get install -y cpio
+        - gzip -cd ../initramfs-kerneltest-full-image-qcom-armv8a.cpio.gz | cpio -idm
+        - gzip -cd ../ramdisk_fastrpc.gz | cpio -idm
+        - find . | cpio -H newc -o | gzip -9 > ../merged-initramfs.cpio.gz
+        - cd ..
+        - mkbootimg --header_version 2 --kernel Image --dtb {{ dtb_name }} --cmdline "console=ttyMSM0,115200n8 earlycon qcom_geni_serial.con_enabled=1 kernel.sched_pelt_multiplier=4 mem_sleep_default=s2idle mitigations=auto video=efifb:off" --ramdisk merged-initramfs.cpio.gz --output boot.img
+    to: downloads
+
+- deploy:
+    images:
+      boot:
+        url: 'downloads://boot.img'
+    timeout:
+      minutes: 2
+    to: download
+
+- boot:
+    prompts:
+    - 'root@[^:]+:~# '
+    failure_retry: 3
+    timeout:
+      minutes: 10
+    timeouts:
+      bootloader-commands:
+        minutes: 3
+      auto-login-action:
+        minutes: 10
+    method: fastboot