test: add rpm stage test for boot_root

Add a stage build test for the boot_root option of the org.osbuild.rpm
stage.  The test defined two manifests that both install the
kernel-uki-virt kernel but differ in the value of the boot_root option.
The diff shows the effect of the value on the install location of the
kernel.

test/data/stages/rpm-kernel-install/a.mpp.yaml

@@ -0,0 +1,32 @@
+---
+version: '2'
+pipelines:
+  - mpp-import-pipelines:
+      path: ../manifests/fedora-vars.ipp.yaml
+  - mpp-import-pipeline:
+      path: ../manifests/fedora-build-v2.ipp.yaml
+      id: build
+    runner:
+      mpp-format-string: org.osbuild.fedora{release}
+  - name: tree
+    build: name:build
+    stages:
+      - type: org.osbuild.rpm
+        inputs:
+          packages:
+            type: org.osbuild.files
+            origin: org.osbuild.source
+            mpp-depsolve:
+              architecture: $arch
+              module-platform-id: $module_platform_id
+              repos:
+                mpp-eval: repos
+              packages:
+                - kernel-uki-virt
+        options:
+          gpgkeys:
+            mpp-eval: gpgkeys
+          exclude:
+            docs: true
+          kernel_install_env:
+            boot_root: "/boot/efi"

test/data/stages/rpm-kernel-install/b.mpp.yaml

@@ -0,0 +1,32 @@
+---
+version: '2'
+pipelines:
+  - mpp-import-pipelines:
+      path: ../manifests/fedora-vars.ipp.yaml
+  - mpp-import-pipeline:
+      path: ../manifests/fedora-build-v2.ipp.yaml
+      id: build
+    runner:
+      mpp-format-string: org.osbuild.fedora{release}
+  - name: tree
+    build: name:build
+    stages:
+      - type: org.osbuild.rpm
+        inputs:
+          packages:
+            type: org.osbuild.files
+            origin: org.osbuild.source
+            mpp-depsolve:
+              architecture: $arch
+              module-platform-id: $module_platform_id
+              repos:
+                mpp-eval: repos
+              packages:
+                - kernel-uki-virt
+        options:
+          gpgkeys:
+            mpp-eval: gpgkeys
+          exclude:
+            docs: true
+          kernel_install_env:
+            boot_root: "/esp"

test/data/stages/rpm-kernel-install/diff.json

@@ -0,0 +1,34 @@
+{
+  "added_files": [
+    "/esp",
+    "/esp/EFI",
+    "/esp/EFI/Linux",
+    "/esp/EFI/Linux/ffffffffffffffffffffffffffffffff-6.11.10-300.fc41.x86_64.efi"
+  ],
+  "deleted_files": [
+    "/boot/efi",
+    "/boot/efi/EFI",
+    "/boot/efi/EFI/Linux",
+    "/boot/efi/EFI/Linux/ffffffffffffffffffffffffffffffff-6.11.10-300.fc41.x86_64.efi"
+  ],
+  "differences": {
+    "/etc/pki/ca-trust/extracted/java/cacerts": {
+      "content": [
+        null,
+        null
+      ]
+    },
+    "/usr/lib/sysimage/rpm/rpmdb.sqlite": {
+      "content": [
+        null,
+        null
+      ]
+    },
+    "/var/cache/ldconfig/aux-cache": {
+      "content": [
+        null,
+        null
+      ]
+    }
+  }
+}