CMake: Load compiler flags from the Serenity repo

Currently, we fail to suppress some warnings on AArch64. Let's use the
tried-and-true flags of a regular Lagom build.

Note that this has the effect of setting some non-warning flags as well
(e.g. `-g1`, `-fno-semantic-interposition`), but they don't hurt us.

Author: BertalanD

CMakeLists.txt

@@ -14,30 +14,6 @@ if (NOT APPLE)
 endif()
 set(CMAKE_INSTALL_RPATH_USE_LINK_PATH TRUE)
 
-# Copied from Serenity's root CMakeLists.txt
-add_compile_options(-Wall)
-add_compile_options(-Wextra)
-add_compile_options(-Wno-address-of-packed-member)
-add_compile_options(-Wcast-align)
-add_compile_options(-Wcast-qual)
-add_compile_options(-Wno-deprecated-copy)
-add_compile_options(-Wduplicated-cond)
-add_compile_options(-Wdouble-promotion)
-add_compile_options(-Wno-expansion-to-defined)
-add_compile_options(-Wformat=2)
-add_compile_options(-Wimplicit-fallthrough)
-add_compile_options(-Wno-literal-suffix)
-add_compile_options(-Wlogical-op)
-add_compile_options(-Wmisleading-indentation)
-add_compile_options(-Wmissing-declarations)
-add_compile_options(-Wno-nonnull-compare)
-add_compile_options(-Wnon-virtual-dtor)
-add_compile_options(-Wno-unknown-warning-option)
-add_compile_options(-Wundef)
-add_compile_options(-Wunused)
-add_compile_options(-Wwrite-strings)
-add_compile_options(-fno-exceptions)
-
 option(ENABLE_ADDRESS_SANITIZER "Enable address sanitizer testing in gcc/clang" OFF)
 option(ENABLE_UNDEFINED_SANITIZER "Enable undefined behavior sanitizer testing in gcc/clang" OFF)
 
@@ -54,3 +30,4 @@ endif()
 include (FetchContent)
 include (cmake/FetchLagom.cmake)
 
+include(${Lagom_SOURCE_DIR}/../CMake/lagom_compile_options.cmake)