github: drop workaround for mold and LTO

Now, ubuntu-24.04 has mold-2.30.0+dfsg-1build1 .
See https://packages.ubuntu.com/noble/mold .

(cherry picked from commit c0b78d2)

Author: yuwata

.github/workflows/build_test.sh

@@ -144,20 +144,11 @@ for args in "${ARGS[@]}"; do
     # It can be safely removed from the CI since it isn't actually used anywhere to test anything.
     find . -type f -name meson.build -exec sed -i '/install_tag/d' '{}' '+'
 
-    # mold < 1.1 does not support LTO.
-    if dpkg --compare-versions "$(dpkg-query --showformat='${Version}' --show mold)" ge 1.1; then
-        fatal "Newer mold version detected, please remove this workaround."
-    elif [[ "$args" == *"-Db_lto=true"* ]]; then
-        LD="gold"
-    else
-        LD="$LINKER"
-    fi
-
     info "Checking build with $args"
     # shellcheck disable=SC2086
     if ! AR="$AR" \
-         CC="$CC" CC_LD="$LD" CFLAGS="$CFLAGS" \
-         CXX="$CXX" CXX_LD="$LD" CXXFLAGS="$CXXFLAGS" \
+         CC="$CC" CC_LD="$LINKER" CFLAGS="$CFLAGS" \
+         CXX="$CXX" CXX_LD="$LINKER" CXXFLAGS="$CXXFLAGS" \
          meson setup \
                -Dtests=unsafe -Dslow-tests=true -Dfuzz-tests=true --werror \
                -Dnobody-group=nogroup -Dcryptolib="${CRYPTOLIB:?}" \