Compilation fails on latest Alpine Linux (missing execinfo.h)

Reproducing the build instructions in the README with the following Dockerfile

```Dockerfile
FROM alpine:3.14

RUN apk add git g++ make cmake unzip libtool curl-dev automake

RUN git clone https://github.com/awslabs/aws-lambda-cpp.git && \
cd aws-lambda-cpp && \
mkdir build && \
cd build && \
cmake .. -DCMAKE_BUILD_TYPE=Release -DCMAKE_INSTALL_PREFIX=~/lambda-install && \
make && make install
```

and running

```bash
docker build -t aws-lambda-cpp .
```

I get

```
#6 0.266 Cloning into 'aws-lambda-cpp'...
#6 1.134 -- The CXX compiler identification is GNU 10.3.1
#6 1.148 -- Detecting CXX compiler ABI info
#6 1.220 -- Detecting CXX compiler ABI info - done
#6 1.236 -- Check for working CXX compiler: /usr/bin/c++ - skipped
#6 1.237 -- Detecting CXX compile features
#6 1.238 -- Detecting CXX compile features - done
#6 1.460 -- Found CURL: /usr/lib/libcurl.so (found version "7.77.0")
#6 1.470 -- Configuring done
#6 1.474 -- Generating done
#6 1.475 -- Build files have been written to: /aws-lambda-cpp/build
#6 1.500 [ 20%] Building CXX object CMakeFiles/aws-lambda-runtime.dir/src/logging.cpp.o
#6 1.630 [ 40%] Building CXX object CMakeFiles/aws-lambda-runtime.dir/src/runtime.cpp.o
#6 2.250 [ 60%] Building CXX object CMakeFiles/aws-lambda-runtime.dir/src/backward.cpp.o
#6 2.340 In file included from /aws-lambda-cpp/src/backward.cpp:26:
#6 2.340 /aws-lambda-cpp/src/backward.h:245:18: fatal error: execinfo.h: No such file or directory
#6 2.340 245 | # include
#6 2.340 | ^~~~~~~~~~~~
#6 2.341 compilation terminated.
#6 2.344 make[2]: *** [CMakeFiles/aws-lambda-runtime.dir/build.make:104: CMakeFiles/aws-lambda-runtime.dir/src/backward.cpp.o] Error 1
#6 2.344 make[1]: *** [CMakeFiles/Makefile2:83: CMakeFiles/aws-lambda-runtime.dir/all] Error 2
#6 2.344 make: *** [Makefile:136: all] Error 2
```

What's missing?

先查看 README 中的构建说明和提供的 Dockerfile，然后检查 execinfo.h include 附近的 src/backward.cpp 和 src/backward.h。使用 Alpine 镜像重现失败，并检查所需的构建依赖或平台条件；当文档中所述的 Docker 构建成功完成时，即表示完成。

由索引模型根据 Issue 内容生成。