[ci] add clang20 and gcc15

Author: h-2

.github/workflows/ci.yml

@@ -54,6 +54,13 @@ jobs:
             build: unit
             build_type: Debug
 
+          - name: "Unit clang20 (libc++)"
+            cxx: "clang++-20"
+            cc: "clang-20"
+            pkg: "clang-20 libc++-20-dev libc++abi-20-dev libc++1-20 libc++abi1-20"
+            cxx_flags: "-std=c++20 -stdlib=libc++"
+            build: unit
+            build_type: Debug
           - name: "Unit gcc11 Release"
             cxx: "g++-11"
             cc: "gcc-11"
@@ -96,6 +103,15 @@ jobs:
             build: unit
             build_type: Debug
 
+          - name: "Unit gcc15 c++23"
+            os: "ubuntu-24.04"
+            cxx: "g++-15"
+            cc: "gcc-15"
+            pkg: "gcc-15 g++-15"
+            cxx_flags: "-std=c++23"
+            build: unit
+            build_type: Debug
+
           - name: "benchmark gcc13"
             cxx: "g++-13"
             cc: "gcc-13"