Add back cxxstd=03 to .drone.jsonnet

Author: pdimov

.drone.jsonnet

@@ -363,35 +363,35 @@ local windows_pipeline(name, image, environment, arch = "amd64") =
     linux_pipeline(
         "Linux 24.04 Clang 18",
         "cppalliance/droneubuntu2404:1",
-        { TOOLSET: 'clang', COMPILER: 'clang++-18', CXXSTD: '11,14,17,20,2b' },
+        { TOOLSET: 'clang', COMPILER: 'clang++-18', CXXSTD: '03,11,14,17,20,2b' },
         "clang-18",
     ),
 
     linux_pipeline(
         "Linux 24.04 Clang 19",
         "cppalliance/droneubuntu2404:1",
-        { TOOLSET: 'clang', COMPILER: 'clang++-18', CXXSTD: '11,14,17,20,2b' },
+        { TOOLSET: 'clang', COMPILER: 'clang++-18', CXXSTD: '03,11,14,17,20,2b' },
         "clang-18",
     ),
 
     linux_pipeline(
         "Linux 24.04 Clang 20 UBSAN",
         "cppalliance/droneubuntu2404:1",
-        { TOOLSET: 'clang', COMPILER: 'clang++-20', CXXSTD: '11,14,17,20,2b' } + ubsan,
+        { TOOLSET: 'clang', COMPILER: 'clang++-20', CXXSTD: '03,11,14,17,20,2b' } + ubsan,
         "clang-20",
     ),
 
     linux_pipeline(
         "Linux 24.04 Clang 20 ASAN",
         "cppalliance/droneubuntu2404:1",
-        { TOOLSET: 'clang', COMPILER: 'clang++-20', CXXSTD: '11,14,17,20,2b' } + asan,
+        { TOOLSET: 'clang', COMPILER: 'clang++-20', CXXSTD: '03,11,14,17,20,2b' } + asan,
         "clang-20",
     ),
 
     linux_pipeline(
         "Linux 25.10 Clang 21",
         "cppalliance/droneubuntu2510:1",
-        { TOOLSET: 'clang', COMPILER: 'clang++-21', CXXSTD: '11,14,17,20,23,2c' },
+        { TOOLSET: 'clang', COMPILER: 'clang++-21', CXXSTD: '03,11,14,17,20,23,2c' },
         "clang-21",
     ),