Pin open source SYCL build workflow to ubuntu-24.04

Author: vlad-perevezentsev

.github/workflows/os-llvm-sycl-build.yml

@@ -10,7 +10,9 @@ permissions:
 jobs:
   install-compiler:
     name: Build with nightly build of DPC++ toolchain
-    runs-on: ubuntu-latest
+    # TODO: back to ubuntu-latest once intel/llvm#23618 is fixed
+    # (nightly ld.lld needs libxml2.so.2, missing on ubuntu-26.04)
+    runs-on: ubuntu-24.04
     timeout-minutes: 90
 
     env: