dev-python/trove-classifiers: Use flit-core, for hatchling bootstrap

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

dev-python/trove-classifiers/trove-classifiers-2023.11.29.ebuild

@@ -3,7 +3,7 @@
 
 EAPI=8
 
-DISTUTILS_USE_PEP517=setuptools
+DISTUTILS_USE_PEP517=flit
 PYPI_NO_NORMALIZE=1
 PYTHON_COMPAT=( pypy3 python3_{10..12} )
 
@@ -19,12 +19,24 @@ LICENSE="Apache-2.0"
 SLOT="0"
 KEYWORDS="~alpha amd64 arm arm64 hppa ~ia64 ~loong ~m68k ~mips ppc ppc64 ~riscv ~s390 sparc x86 ~amd64-linux ~x86-linux ~arm64-macos ~ppc-macos ~x64-macos ~x64-solaris"
 
-BDEPEND="
-	dev-python/calver[${PYTHON_USEDEP}]
-"
-
 distutils_enable_tests pytest
 
+src_configure() {
+	grep -q 'build-backend = "setuptools' pyproject.toml ||
+		die "Upstream changed build-backend, recheck"
+	# write a custom pyproject.toml to ease hatchling bootstrap
+	cat > pyproject.toml <<-EOF || die
+		[build-system]
+		requires = ["flit_core >=3.2,<4"]
+		build-backend = "flit_core.buildapi"
+
+		[project]
+		name = "trove-classifiers"
+		version = "${PV}"
+		description = "Canonical source for classifiers on PyPI (pypi.org)."
+	EOF
+}
+
 python_test() {
 	epytest
 	"${EPYTHON}" -m tests.lib || die