Ladybird/Meta: Convert to CMake build

Ladybird/README.md

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+# Ladybird Web Browser
+
+The Ladybird Web Browser is a browser using the SerenityOS LibWeb engine with a QT GUI.
+
+## Build Prerequisites
+
+QT6 development packages and a c++20-enabled compiler are required. On Debian/Ubuntu required packages include, but are not limited to:
+
+```
+sudo apt install build-essential cmake ninja-build qt6-base-dev qt6-tools-dev-tools
+```
+
+For the c++ compiler, gcc-11 or clang-13 are required at a minimum for c++20 support.
+
+For Ubuntu 20.04 and above, ensure that the QT6 Wayland packages are available:
+
+```
+sudo apt install qt6-wayland
+```
+
+
+## Build steps
+
+Basic workflow, using serenity source dir cloned from github:
+
+```
+cmake -GNinja -B Build
+cmake --build Build
+ninja -C Build run
+```
+
+Advanced workflow, using pre-existing serenity checkout.
+
+If you previously didn't set SERENITY_SOURCE_DIR, probably want to blast the Build directory before doing this:
+
+```
+cmake -GNinja -B Build -DSERENITY_SOURCE_DIR=/path/to/serenity
+ninja -C Build run
+```
+
+To automatically run in gdb:
+```
+ninja -C Build debug
+```
+
+To run without ninja rule:
+```
+# or your existing serenity checkout /path/to/serenity
+export SERENITY_SOURCE_DIR=${PWD}/Build/serenity
+./Build/ladybird
+```