关于新的NDK编译Openssl时候，遇到gcc文件不存在的问题处理

自从NDK的r19开始，由于gcc兼容clang的编译方式有问题，该版本已经移除了相关gcc文件，所以用老方法交叉编译Openssl的时候，会提示找不到gcc文件。
实际现在是直接使用clang编译即可，具体方法如下：
1.下载NDK
https://developer.android.com/ndk/downloads/index.html
2.下载openssl
https://www.openssl.org/source/

3.设置相关环境变量

# Set directory
SCRIPTPATH=`realpath .`
export ANDROID_NDK_HOME=$SCRIPTPATH/android-ndk-r20
OPENSSL_DIR=$SCRIPTPATH/openssl-1.1.1c

4.建立toolchains_path.py来获取设置toolchains_path

#!/usr/bin/env python
"""
    Get the toolchains path
"""
import argparse
import atexit
import inspect
import os
import shutil
import stat
import sys
import textwrap

def get_host_tag_or_die():
    """Return the host tag for this platform. Die if not supported."""
    if sys.platform.startswith('linux'):
        return 'linux-x86_64'
    elif sys.platform == 'darwin':
        return 'darwin-x86_64'
    elif sys.platform == 'win32' or sys.platform == 'cygwin':
        host_tag = 'windows-x86_64'
        if not os.path.exists(os.path.join(NDK_DIR, 'prebuilt', host_tag)):
            host_tag = 'windows'
        return host_tag
    sys.exit('Unsupported platform: ' + sys.platform)


def get_toolchain_path_or_die(ndk, host_tag):
    """Return the toolchain path or die."""
    toolchain_path = os.path.join(ndk, 'toolchains/llvm/prebuilt',
                                  host_tag)
    if not os.path.exists(toolchain_path):
        sys.exit('Could not find toolchain: {}'.format(toolchain_path))
    return toolchain_path

def main():
    """Program entry point."""
    parser = argparse.ArgumentParser(description='Optional app description')
    parser.add_argument('--ndk', required=True,
                    help='The NDK Home directory')
    args = parser.parse_args()

    host_tag = get_host_tag_or_die()
    toolchain_path = get_toolchain_path_or_die(args.ndk, host_tag)
    print toolchain_path

if __name__ == '__main__':
    main()

5.设置toolchains_path

toolchains_path=$(python toolchains_path.py --ndk ${ANDROID_NDK_HOME})

6.进行OPENSSL环境配置

# Set compiler clang, instead of gcc by default
CC=clang# Add toolchains bin directory to PATH
PATH=$toolchains_path/bin:$PATH# Set the Android API levels
ANDROID_API=21# Set the target architecture
# Can be android-arm, android-arm64, android-x86, android-x86 etc
architecture=android-arm

7.make file

# Create the make file
cd ${OPENSSL_DIR}
./Configure ${architecture} -D__ANDROID_API__=$ANDROID_API

8.build

make

9.拷贝到对应目录

# Copy the outputs
OUTPUT_INCLUDE=$SCRIPTPATH/output/include
OUTPUT_LIB=$SCRIPTPATH/output/lib/${architecture}
mkdir -p $OUTPUT_INCLUDE
mkdir -p $OUTPUT_LIB
cp -RL include/openssl $OUTPUT_INCLUDE
cp libcrypto.so $OUTPUT_LIB
cp libcrypto.a $OUTPUT_LIB
cp libssl.so $OUTPUT_LIB

10.以上的代码整合到一个脚本如下：

#!/bin/bash
set -e
set -x

# Set directory
SCRIPTPATH=`realpath .`
export ANDROID_NDK_HOME=$SCRIPTPATH/android-ndk-r20
OPENSSL_DIR=$SCRIPTPATH/openssl-1.1.1c

# Find the toolchain for your build machine
toolchains_path=$(python toolchains_path.py --ndk ${ANDROID_NDK_HOME})

# Configure the OpenSSL environment, refer to NOTES.ANDROID in OPENSSL_DIR
# Set compiler clang, instead of gcc by default
CC=clang

# Add toolchains bin directory to PATH
PATH=$toolchains_path/bin:$PATH

# Set the Android API levels
ANDROID_API=21

# Set the target architecture
# Can be android-arm, android-arm64, android-x86, android-x86 etc
architecture=android-arm

# Create the make file
cd ${OPENSSL_DIR}
./Configure ${architecture} -D__ANDROID_API__=$ANDROID_API

# Build
make

# Copy the outputs
OUTPUT_INCLUDE=$SCRIPTPATH/output/include
OUTPUT_LIB=$SCRIPTPATH/output/lib/${architecture}
mkdir -p $OUTPUT_INCLUDE
mkdir -p $OUTPUT_LIB
cp -RL include/openssl $OUTPUT_INCLUDE
cp libcrypto.so $OUTPUT_LIB
cp libcrypto.a $OUTPUT_LIB
cp libssl.so $OUTPUT_LIB
cp libssl.a $OUTPUT_LIB

具体参考Tutorial: Compile OpenSSL 1.1.1 for Android application