Add Zstd support through meson (#2293)

* Add Zstd support through meson

* Add libzstd-dev to abitest

.github/workflows/abidiff.yaml

@@ -29,6 +29,7 @@ jobs:
         git
         libbrotli-dev
         libssl-dev
+        libzstd-dev
         meson
         pkg-config
         python3

meson.build

@@ -74,6 +74,12 @@ if brotli_found_all
   args += '-DCPPHTTPLIB_BROTLI_SUPPORT'
 endif
 
+zstd_dep = dependency('libzstd', required: get_option('zstd'))
+if zstd_dep.found()
+  deps += zstd_dep
+  args += '-DCPPHTTPLIB_ZSTD_SUPPORT'
+endif
+
 async_ns_opt = get_option('non_blocking_getaddrinfo')
 
 if host_machine.system() == 'windows'

meson_options.txt

@@ -5,6 +5,7 @@
 option('openssl', type: 'feature', value: 'auto', description: 'Enable OpenSSL support')
 option('zlib',    type: 'feature', value: 'auto', description: 'Enable zlib support')
 option('brotli',  type: 'feature', value: 'auto', description: 'Enable Brotli support')
+option('zstd',    type: 'feature', value: 'auto', description: 'Enable zstd support')
 option('macosx_keychain', type: 'feature', value: 'auto', description: 'Enable loading certs from the Keychain on Apple devices')
 option('non_blocking_getaddrinfo', type: 'feature', value: 'auto', description: 'Enable asynchronous name lookup')
 option('compile', type: 'boolean', value: false,  description: 'Split the header into a compilable header & source file (requires python3)')