Kernel+Toolchain: Use `.init_array` section for global constructors

Before this change, our dynamic linker's global constructor handler
relied on the GNU linker implicitly including the content of `.ctors`
section inside `.init_array`. The mold linker does not do this, so
global constructors would fail to be called in the mold-built userland.

There is no point in sticking to `.ctors`, as most other systems already
use the superior `.init_array` scheme. This commit changes the kernel
linker script to not discard this new section, and enables it by default
in our toolchain.

Kernel/linker.ld

@@ -59,10 +59,12 @@ SECTIONS
     {
         start_heap_ctors = .;
         *libkernel_heap.a:*(.ctors)
+        *libkernel_heap.a:*(.init_array)
         end_heap_ctors = .;
 
         start_ctors = .;
         *(.ctors)
+        *(.init_array)
         end_ctors = .;
 
         *(.rodata*)

Ports/gcc/package.sh

@@ -2,7 +2,7 @@
 port=gcc
 version=11.2.0
 useconfigure=true
-configopts=("--target=${SERENITY_ARCH}-pc-serenity" "--with-sysroot=/" "--with-build-sysroot=${SERENITY_INSTALL_ROOT}" "--with-newlib" "--enable-languages=c,c++" "--disable-lto" "--disable-nls" "--enable-shared" "--enable-default-pie" "--enable-host-shared" "--enable-threads=posix")
+configopts=("--target=${SERENITY_ARCH}-pc-serenity" "--with-sysroot=/" "--with-build-sysroot=${SERENITY_INSTALL_ROOT}" "--with-newlib" "--enable-languages=c,c++" "--disable-lto" "--disable-nls" "--enable-shared" "--enable-default-pie" "--enable-host-shared" "--enable-threads=posix" "--enable-initfini-array")
 files="https://ftpmirror.gnu.org/gnu/gcc/gcc-${version}/gcc-${version}.tar.xz gcc-${version}.tar.xz d08edc536b54c372a1010ff6619dd274c0f1603aa49212ba20f7aa2cda36fa8b"
 makeopts=("all-gcc" "all-target-libgcc" "all-target-libstdc++-v3" "-j$(nproc)")
 installopts=("DESTDIR=${SERENITY_INSTALL_ROOT}" "install-gcc" "install-target-libgcc" "install-target-libstdc++-v3")

Toolchain/BuildIt.sh

@@ -379,6 +379,7 @@ pushd "$DIR/Build/$ARCH"
                                             --enable-default-pie \
                                             --enable-lto \
                                             --enable-threads=posix \
+                                            --enable-initfini-array \
                                             ${TRY_USE_LOCAL_TOOLCHAIN:+"--quiet"} || exit 1
 
         echo "XXX build gcc and libgcc"