Meta: Add an option to precompile some very common AK headers

Until we get the goodness that C++ modules are supposed to be, let's try
to shave off some parse time using precompiled headers.
This commit only adds some very common AK headers, only to binaries,
libraries and the kernel (tests are not covered due to incompatibility
with AK/TestSuite.h).
This option is on by default, but can be disabled by passing
`-DPRECOMPILE_COMMON_HEADERS=OFF` to cmake, which will disable all
header precompilations.
This makes the build about 30 seconds faster on my machine (about 7%).

CMakeLists.txt

@@ -26,6 +26,7 @@ option(ENABLE_ALL_THE_DEBUG_MACROS "Enable all debug macros to validate they sti
 option(ENABLE_COMPILETIME_FORMAT_CHECK "Enable compiletime format string checks" ON)
 option(ENABLE_PCI_IDS_DOWNLOAD "Enable download of the pci.ids database at build time" ON)
 option(BUILD_LAGOM "Build parts of the system targeting the host OS for fuzzing/testing" OFF)
+option(PRECOMPILE_COMMON_HEADERS "Precompile some common headers to speedup compilation" ON)
 
 add_custom_target(run
     COMMAND ${CMAKE_SOURCE_DIR}/Meta/run.sh

Kernel/CMakeLists.txt

@@ -361,6 +361,7 @@ add_executable(Kernel ${SOURCES})
 target_link_libraries(Kernel kernel_heap gcc stdc++)
 add_dependencies(Kernel boot kernel_heap)
 install(TARGETS Kernel RUNTIME DESTINATION boot)
+serenity_add_ak_precompiled_headers_to_target(Kernel)
 
 add_custom_command(
     TARGET Kernel

Meta/CMake/precompile-headers.cmake

@@ -0,0 +1,9 @@
+function(serenity_add_precompiled_header_to_target target header)
+    if (PRECOMPILE_COMMON_HEADERS AND COMMAND target_precompile_headers)
+        target_precompile_headers(${target} PRIVATE ${header})
+    endif ()
+endfunction()
+
+function(serenity_add_ak_precompiled_headers_to_target target)
+    serenity_add_precompiled_header_to_target(${target} ${CMAKE_SOURCE_DIR}/Meta/Precompile/AK.h)
+endfunction()

Meta/CMake/utils.cmake

@@ -1,3 +1,5 @@
+include(${CMAKE_SOURCE_DIR}/Meta/CMake/precompile-headers.cmake)
+
 function(serenity_install_headers target_name)
     file(GLOB_RECURSE headers RELATIVE ${CMAKE_CURRENT_SOURCE_DIR} "*.h")
     foreach(header ${headers})
@@ -31,6 +33,7 @@ function(serenity_lib target_name fs_name)
     add_library(${target_name} SHARED ${SOURCES} ${GENERATED_SOURCES})
     install(TARGETS ${target_name} DESTINATION usr/lib)
     set_target_properties(${target_name} PROPERTIES OUTPUT_NAME ${fs_name})
+    serenity_add_ak_precompiled_headers_to_target(${target_name})
     serenity_generated_sources(${target_name})
 endfunction()
 
@@ -67,6 +70,7 @@ endfunction()
 function(serenity_bin target_name)
     add_executable(${target_name} ${SOURCES})
     install(TARGETS ${target_name} RUNTIME DESTINATION bin)
+    serenity_add_ak_precompiled_headers_to_target(${target_name})
     serenity_generated_sources(${target_name})
 endfunction()
 

Meta/Precompile/AK.h

@@ -0,0 +1,48 @@
+/*
+ * Copyright (c) 2021, Ali Mohammad Pur <ali.mpfard@gmail.com>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#pragma once
+
+#include <AK/Assertions.h>
+#include <AK/Badge.h>
+#include <AK/ByteBuffer.h>
+#include <AK/Format.h>
+#include <AK/Forward.h>
+#include <AK/Function.h>
+#include <AK/HashMap.h>
+#include <AK/JsonObject.h>
+#include <AK/LexicalPath.h>
+#include <AK/Optional.h>
+#include <AK/OwnPtr.h>
+#include <AK/RefCounted.h>
+#include <AK/RefPtr.h>
+#include <AK/StdLibExtras.h>
+#include <AK/String.h>
+#include <AK/StringBuilder.h>
+#include <AK/StringView.h>
+#include <AK/Types.h>
+#include <AK/URL.h>
+#include <AK/Vector.h>