Meta: Update to clang-19 in CI and build instructions

Author: https://github.com/trflynn89
Commit: 2ec97b4548
Pull-request: https://github.com/LadybirdBrowser/ladybird/pull/3067

.devcontainer/devcontainer.json

@@ -6,7 +6,7 @@
         "ghcr.io/devcontainers/features/github-cli:1": {},
         "ghcr.io/devcontainers-contrib/features/pre-commit:2": {},
         "./features/ladybird": {
-            "llvm_version": 18
+            "llvm_version": 19
         },
         "./features/vcpkg-cache": {
             "release_triplet": true,
@@ -70,7 +70,7 @@
                 "git.inputValidationSubjectLength": 72,
                 // If clangd was obtained from a package manager, its path can be set here.
                 // Note: This has to be adjusted manually, to the "llvm_version" from above
-                "clangd.path": "clangd-18",
+                "clangd.path": "clangd-19",
                 "clangd.arguments": [
                     "--header-insertion=never" // See https://github.com/clangd/clangd/issues/1247
                 ]

.devcontainer/features/ladybird/devcontainer-feature.json

@@ -12,7 +12,7 @@
                 19,
                 "trunk"
             ],
-            "default": 18,
+            "default": 19,
             "description": "Select LLVM compiler version to use"
         }
     }

.devcontainer/features/ladybird/install.sh

@@ -3,7 +3,7 @@ set -e
 
 # Feature options
 
-LLVM_VERSION=${LLVM_VERSION:-18}
+LLVM_VERSION=${LLVM_VERSION:-19}
 ### Check distro
 
 if [ ! -f /etc/lsb-release ]; then