Add c++20 builder

evergreen/config.yml

@@ -88,6 +88,10 @@ functions:
               set_cmake_var compiler_vars CMAKE_CXX_COMPILER PATH $(./evergreen/abspath.sh "${cxx_compiler}")
           fi
 
+          if [ -n "${cxx_standard|}" ]; then
+              set_cmake_var realm_vars CMAKE_CXX_STANDARD STRING "${cxx_standard}"
+          fi
+
           if [[ -z "${disable_tests_against_baas|}" && -z "${no_tests|}" ]]; then
               scheme="http"
               set_cmake_var baas_vars REALM_ENABLE_AUTH_TESTS BOOL On
@@ -1218,6 +1222,16 @@ tasks:
       display_name: changeset dump tarball
 
 task_groups:
+- name: compile_only
+  setup_group_can_fail_task: true
+  setup_group:
+  - func: "fetch source"
+  - func: "fetch binaries"
+  timeout:
+  - func: "run hang analyzer"
+  tasks:
+  - compile
+
 - name: core_tests_group
   setup_group_can_fail_task: true
   setup_group:
@@ -1591,6 +1605,17 @@ buildvariants:
   tasks:
   - name: compile_test
 
+- name: ubuntu-cxx20
+  display_name: "Ubuntu (c++20)"
+  run_on: ubuntu2204-arm64-large
+  expansions:
+    fetch_missing_dependencies: On
+    cxx_standard: 20
+    c_compiler: "/opt/clang+llvm/bin/clang"
+    cxx_compiler: "/opt/clang+llvm/bin/clang++"
+  tasks:
+  - name: compile_only
+
 - name: ubuntu-fuzzer
   display_name: "Ubuntu (Fuzzer)"
   run_on: ubuntu2204-arm64-large