meson.build: add HAVE_GLIB_WITH_ALIGNED_ALLOC flag

Rust crates, introduced from the next commit onwards, can optionally use
the glib allocator API and need to know whether g_aligned_alloc etc are
available.

This commit adds a define in config_host_data that depends on glib
version >= 2.72.

Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Manos Pitsidianakis <manos.pitsidianakis@linaro.org>
Link: https://lore.kernel.org/r/23f7b0cc9801d315f5d7835e30d775e133ec2fb9.1727961605.git.manos.pitsidianakis@linaro.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

meson.build

@@ -948,7 +948,9 @@ have_xen_pci_passthrough = get_option('xen_pci_passthrough') \
 ################
 
 # When bumping glib minimum version, please check also whether to increase
-# the _WIN32_WINNT setting in osdep.h according to the value from glib
+# the _WIN32_WINNT setting in osdep.h according to the value from glib.
+# You should also check if any of the glib.version() checks
+# below can also be removed.
 glib_req_ver = '>=2.66.0'
 glib_pc = dependency('glib-2.0', version: glib_req_ver, required: true,
                     method: 'pkg-config')
@@ -998,6 +1000,9 @@ glib = declare_dependency(dependencies: [glib_pc, gmodule],
 # TODO: remove this check and the corresponding workaround (qtree) when
 # the minimum supported glib is >= 2.75.3
 glib_has_gslice = glib.version().version_compare('<2.75.3')
+# Check whether glib has the aligned_alloc family of functions.
+# <https://docs.gtk.org/glib/func.aligned_alloc.html>
+glib_has_aligned_alloc = glib.version().version_compare('>=2.72.0')
 
 # override glib dep to include the above refinements
 meson.override_dependency('glib-2.0', glib)
@@ -2529,6 +2534,7 @@ config_host_data.set('CONFIG_TIMERFD', cc.has_function('timerfd_create'))
 config_host_data.set('HAVE_COPY_FILE_RANGE', cc.has_function('copy_file_range'))
 config_host_data.set('HAVE_GETIFADDRS', cc.has_function('getifaddrs'))
 config_host_data.set('HAVE_GLIB_WITH_SLICE_ALLOCATOR', glib_has_gslice)
+config_host_data.set('HAVE_GLIB_WITH_ALIGNED_ALLOC', glib_has_aligned_alloc)
 config_host_data.set('HAVE_OPENPTY', cc.has_function('openpty', dependencies: util))
 config_host_data.set('HAVE_STRCHRNUL', cc.has_function('strchrnul'))
 config_host_data.set('HAVE_SYSTEM_FUNCTION', cc.has_function('system', prefix: '#include <stdlib.h>'))