Fix unsupported std values and ARM clang runner

Author: igaztanaga

.github/workflows/ci.yml

@@ -310,7 +310,7 @@ jobs:
           # Linux, clang-15
           - toolset: clang
             compiler: clang++-15
-            cxxstd: "03,11,14,17,20,23"
+            cxxstd: "03,11,14,17,20,2b"
             cxxflags: -pipe
             container: ubuntu:22.04
             os: ubuntu-latest
@@ -319,7 +319,7 @@ jobs:
           - toolset: clang
             compiler: clang++-16
             cxxflags: -pipe
-            cxxstd: "03,11,14,17,20,23"
+            cxxstd: "03,11,14,17,20,2b"
             container: ubuntu:24.04
             os: ubuntu-latest
             install: clang-16
@@ -374,7 +374,7 @@ jobs:
           # Linux, clang-15 libc++
           - toolset: clang
             compiler: clang++-15
-            cxxstd: "11,14,17,20,23"
+            cxxstd: "11,14,17,20,2b"
             os: ubuntu-latest
             container: ubuntu:22.04
             install:
@@ -446,7 +446,9 @@ jobs:
             cxxstd: "03,11,14,17,20,23,26"
             cxxflags: -pipe
             os: ubuntu-26.04-arm
-            install: clang
+            install:
+              - clang
+              - g++
           #------------------
           # MacOS, clang
           #------------------