zstd: Add CMake build system

Although the upstream has a CMake build system, it is meant for the
complete package.  Add a simple one to build just the static library
we need within CMake.

Utilities/cmzstd/CMakeLists.txt

+project(zstd C)
+
+# Disable warnings to avoid changing 3rd party code.
+if(CMAKE_C_COMPILER_ID MATCHES
+    "^(GNU|Clang|AppleClang|XLClang|XL|VisualAge|SunPro|HP|Intel)$")
+  set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -w")
+elseif(CMAKE_C_COMPILER_ID STREQUAL "PathScale")
+  set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -woffall")
+endif()
+
+include_directories(lib lib/common)
+
+add_library(cmzstd STATIC
+  lib/common/entropy_common.c
+  lib/common/error_private.c
+  lib/common/fse_decompress.c
+  lib/common/pool.c
+  lib/common/threading.c
+  lib/common/xxhash.c
+  lib/common/zstd_common.c
+  lib/compress/fse_compress.c
+  lib/compress/hist.c
+  lib/compress/huf_compress.c
+  lib/compress/zstd_compress.c
+  lib/compress/zstd_double_fast.c
+  lib/compress/zstd_fast.c
+  lib/compress/zstd_lazy.c
+  lib/compress/zstd_ldm.c
+  lib/compress/zstdmt_compress.c
+  lib/compress/zstd_opt.c
+  lib/decompress/huf_decompress.c
+  lib/decompress/zstd_ddict.c
+  lib/decompress/zstd_decompress_block.c
+  lib/decompress/zstd_decompress.c
+  lib/deprecated/zbuff_common.c
+  lib/deprecated/zbuff_compress.c
+  lib/deprecated/zbuff_decompress.c
+  lib/dictBuilder/cover.c
+  lib/dictBuilder/divsufsort.c
+  lib/dictBuilder/fastcover.c
+  lib/dictBuilder/zdict.c
+  )
+
+install(FILES LICENSE DESTINATION ${CMAKE_DOC_DIR}/cmzstd)