dev-python/multidict: Add a flag to disable C extensions entirely

Signed-off-by: Michał Górny <mgorny@gentoo.org>

dev-python/multidict/metadata.xml

@@ -13,4 +13,10 @@
 		<remote-id type="github">aio-libs/multidict</remote-id>
 		<remote-id type="pypi">multidict</remote-id>
 	</upstream>
+	<use>
+		<flag name="native-extensions">
+			Compile native C extensions (speedups, instead of using Python
+			fallback code).
+		</flag>
+	</use>
 </pkgmetadata>

dev-python/multidict/multidict-6.0.4-r1.ebuild

@@ -22,6 +22,7 @@ SRC_URI="
 LICENSE="Apache-2.0"
 SLOT="0"
 KEYWORDS="~alpha amd64 arm arm64 hppa ~ia64 ~loong ppc ppc64 ~riscv ~s390 sparc x86 ~x64-macos"
+IUSE="+native-extensions"
 
 distutils_enable_sphinx docs --no-autodoc
 distutils_enable_tests pytest
@@ -36,7 +37,7 @@ python_prepare_all() {
 python_compile() {
 	# the C extension segfaults on py3.12
 	# https://github.com/aio-libs/multidict/issues/868
-	if [[ ${EPYTHON} == python3.12 ]]; then
+	if ! use native-extensions || [[ ${EPYTHON} == python3.12 ]]; then
 		local -x MULTIDICT_NO_EXTENSIONS=1
 	fi