1. Disable zlib _explictly_ when building libcurl in remote attestaion demo.
The reason for this is that zlib may be implictly linked by the build system of
libcurl but not the zlib library is not copied into the Occlum FS image.
2. Use `make -j$(nproc)`
3. Fix typos
This demo consists of
1. An user-friendly library for getting Intel Attestation Service (IAS) report.
2. A application that uses this library to get IAS report.
This demo requires obtaining service provider certificate/ID from Intel.
This commit makes the toolchain easier to use in two folds:
1. When compiling C/C++ source files, no need to add "-fPIC -pie" flags manually;
2. When running executables generated by the Occlum toolchain on Linux, no
need to set the `LD_LIBRARY_PATH` manually.
