[util-chroot] enalble lto by default

• Enable link time optimization (LTO) of packages by default by adding the -flto flag. This provides smaller, faster executables/DSOs, and improves GCC diagnostics.
• Arch didn't enable it in pacman package, hence add it here
• see also: https://gitlab.archlinux.org/archlinux/devtools/-/commit/16b7a0e7e8ef795621172cb08887a2f86f0b0222
• see also: https://gitlab.manjaro.org/yochananmarqos1/manjaro-chrootbuild/-/commit/8ea4e8daa1f4b672bd61c57ccbcab7e3d37679c4