tests: run upstream llvm integration testsuite with python-lit

tests/build-gating.fmf

@@ -10,7 +10,7 @@
 #   * RHEL-7 (software collection)
 #
 
-summary: compiler-rt tests for build/PR gating
+summary: python-lit tests for build/PR gating
 adjust:
   - because: "Plan to be ran when either executed locally, or executed by CI system to gate a build or PR."
     when: >-
@@ -21,13 +21,45 @@ adjust:
 
   - because: "When testing SCL-ized LLVM, the collection must be enabled first"
     environment+:
-      WITH_SCL: "scl enable llvm-toolset-13.0 rust-toolset-1.58"
+      WITH_SCL: "scl enable llvm-toolset-13.0"
     when: "collection == llvm-toolset-13.0"
 
+  # Unfortunately, TMT does not support more declarative approach, we need to run commands on our own.
+  - because: "On RHEL, CRB must be enabled to provide rarer packages"
+    when: >-
+      distro == rhel-9
+      or distro == rhel-8
+    prepare+:
+      - name: Enable CRB
+        how: shell
+        script: dnf config-manager --set-enabled rhel-CRB
+
+  - because: "On CentOS, CRB must be enabled to provide rarer packages"
+    when: >-
+      distro == centos
+    prepare+:
+      - name: Enable CRB
+        how: shell
+        script: dnf config-manager --set-enabled crb
+
+  # Unfortunately, TMT does not support more declarative approach, we need to run commands on our own.
+  - because: "On RHEL-7, EPEL must be enabled to provided rarer packages"
+    prepare+:
+      - name: Enable EPEL
+        how: shell
+        script: |
+          rpm -q epel-release || yum install -y https://dl.fedoraproject.org/pub/epel/epel-release-latest-7.noarch.rpm
+          yum-config-manager --enable epel
+    when: distro == rhel-7
+
 discover:
     - name: python-lit-tests
       how: fmf
-      filter: "tag:-spoils-installation"
+    - name: upstream-llvm-integration-testsuite
+      how: fmf
+      url: https://src.fedoraproject.org/rpms/llvm.git
+      ref: rawhide
+      test: integration-test-suite
 execute:
     how: tmt
 provision: