meson.build: Disable zlib as per -Dzlib option

Disable use of zlib as per -Dzlib option.
Default value is true. To disable zlib usage, specify -Dzlib=false

Reviewed-by: Charmaine Lee <charmainel@vmware.com>
Reviewed-by: Zack Rusin <zackr@vmware.com
Reviewed-by: Jose Fonseca <jfonseca@vmware.com>
Reviewed-by: Erik Faye-Lund <erik.faye-lund@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/7806>

meson.build

@@ -1371,9 +1371,12 @@ else
   dep_clock = cc.find_library('rt')
 endif
 
-# TODO: some of these may be conditional
-dep_zlib = dependency('zlib', version : '>= 1.2.3', fallback : ['zlib', 'zlib_dep'])
-pre_args += '-DHAVE_ZLIB'
+dep_zlib = dependency('zlib', version : '>= 1.2.3',
+                      fallback : ['zlib', 'zlib_dep'],
+                      required : get_option('zlib'))
+if dep_zlib.found()
+  pre_args += '-DHAVE_ZLIB'
+endif
 
 _zstd = get_option('zstd')
 if _zstd == 'true'

meson_options.txt

@@ -441,6 +441,12 @@ option(
   value : 'auto',
   description : 'Use ZSTD instead of ZLIB in some cases.'
 )
+option(
+   'zlib',
+   type : 'feature',
+   value : 'enabled',
+   description : 'Use ZLIB to build driver. Default: enabled'
+)
 option(
   'sse2',
   type : 'boolean',