build: suppress array-bounds errors in libxkbcommon

These occur when building with GCC 12.1.

It might be the case that these would be suppressed by updating the
package, but that would also require installing new build tools (meson),
as well as potentially more dependencies (wayland).

```bash
In function 'ExprCreateBoolean',
    inlined from 'BoolVarCreate' at src/xkbcomp/ast-build.c:316:19:
src/xkbcomp/ast-build.c:119:23: error: array subscript 'ExprDef[0]' is partly outside array bounds of 'unsigned char[32]' [-Werror=array-bounds]
  119 |     expr->boolean.set = set;
      |     ~~~~~~~~~~~~~~~~~~^~~~~
In function 'ExprCreate',
    inlined from 'ExprCreateBoolean' at src/xkbcomp/ast-build.c:118:5,
    inlined from 'BoolVarCreate' at src/xkbcomp/ast-build.c:316:19:
src/xkbcomp/ast-build.c:75:21: note: object of size 32 allocated by 'malloc'
   75 |     ExprDef *expr = malloc(size);
      |                     ^~~~~~~~~~~~
```

depends/packages/libxkbcommon.mk

@@ -5,9 +5,14 @@ $(package)_file_name=$(package)-$($(package)_version).tar.xz
 $(package)_sha256_hash=60ddcff932b7fd352752d51a5c4f04f3d0403230a584df9a2e0d5ed87c486c8b
 $(package)_dependencies=libxcb
 
+# This package explicitly enables -Werror=array-bounds, which causes build failures
+# with GCC 12.1+. Work around that by turning errors back into warnings.
+# This workaround would be dropped if the package was updated, as that would require
+# a different build system (Meson)
 define $(package)_set_vars
 $(package)_config_opts = --enable-option-checking --disable-dependency-tracking
 $(package)_config_opts += --disable-static --disable-docs
+$(package)_cflags += -Wno-error=array-bounds
 endef
 
 define $(package)_preprocess_cmds