GH-46679: [C++][Meson] Use WrapDB entry for gflags instead of CMake wrapper (#46680)

### Rationale for this change

By using the wrapdb entry for gflags, we can use a Meson-native solution for wrapping that project without requiring CMake

### What changes are included in this PR?

Switched to using the WrapDB entry for gflags

### Are these changes tested?

Yes

### Are there any user-facing changes?

No
* GitHub Issue: #46679

Authored-by: Will Ayd <[email protected]>
Signed-off-by: Sutou Kouhei <[email protected]>

Author: WillAyd

cpp/subprojects/gflags.wrap

@@ -20,7 +20,11 @@ source_url = https://github.com/gflags/gflags/archive/refs/tags/v2.2.2.tar.gz
 source_filename = gflags-2.2.2.tar.gz
 source_hash = 34af2f15cf7367513b352bdcd2493ab14ce43692d2dcd9dfc499492966c64dcf
 directory = gflags-2.2.2
-method = cmake
+patch_filename = gflags_2.2.2-1_patch.zip
+patch_url = https://wrapdb.mesonbuild.com/v2/gflags_2.2.2-1/get_patch
+patch_hash = 7988220486c98f2749db713b204ee6c009be04b67932783ffad7acdf3e334f19
+source_fallback_url = https://github.com/mesonbuild/wrapdb/releases/download/gflags_2.2.2-1/gflags-2.2.2.tar.gz
+wrapdb_version = 2.2.2-1
 
 [provide]
-gflags = gflags_static_dep
+gflags = gflags_dep