libc/elf: rename modlib to libelf

Renaming "modlib" to "libelf" is more in line with the implementation content,
which makes it easier for individual developers to understand the capabilities of this module.

CONFIG_LIBC_MODLIB -> CONFIG_LIBC_ELF

Signed-off-by: chao an <anchao.archer@bytedance.com>

libs/libc/elf/Make.defs

@@ -0,0 +1,41 @@
+############################################################################
+# libs/libc/elf/Make.defs
+#
+# SPDX-License-Identifier: Apache-2.0
+#
+# Licensed to the Apache Software Foundation (ASF) under one or more
+# contributor license agreements.  See the NOTICE file distributed with
+# this work for additional information regarding copyright ownership.  The
+# ASF licenses this file to you under the Apache License, Version 2.0 (the
+# "License"); you may not use this file except in compliance with the
+# License.  You may obtain a copy of the License at
+#
+#   http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the
+# License for the specific language governing permissions and limitations
+# under the License.
+#
+############################################################################
+
+ifeq ($(CONFIG_LIBC_ELF),y)
+
+# Add the nuttx/lib/elf.h files to the build
+
+CSRCS += elf_addrenv.c elf_bind.c elf_depend.c elf_init.c
+CSRCS += elf_iobuffer.c elf_load.c elf_loadhdrs.c elf_verify.c
+CSRCS += elf_read.c elf_registry.c elf_sections.c
+CSRCS += elf_symbols.c elf_symtab.c elf_uninit.c elf_unload.c
+CSRCS += elf_gethandle.c elf_getsymbol.c elf_insert.c
+CSRCS += elf_remove.c
+
+# Add the elf directory to the build
+
+ASRCS += elf_globals.S
+
+DEPPATH += --dep-path elf
+VPATH += :elf
+
+endif