llvm-core/flang: Add 21.0.0_pre20250215 snapshot

Closes: https://bugs.gentoo.org/748087
Signed-off-by: Michał Górny <mgorny@gentoo.org>

llvm-core/flang/Manifest

@@ -0,0 +1 @@
+DIST llvm-project-c30a7f459452d5766da244564bc1d5888346c364.tar.gz 227560986 BLAKE2B c1c833aa6d488530826d96db81ca8be2fcf842ccf5b10a65ff18269fdfa32fa2742fb0a547eb315c2a9ee383e1b6b6cce4a78136e1740e04d322c79fb6a66a86 SHA512 0b68d3462e5eac89f50cff5e64603758ab74c701ff2de88c8569dd45b7e702b5d13b26c2745615c0c355d46d13765f47e4d43e61cde735240c6f386c0090becb

llvm-core/flang/flang-21.0.0_pre20250215.ebuild

@@ -0,0 +1,72 @@
+# Copyright 1999-2025 Gentoo Authors
+# Distributed under the terms of the GNU General Public License v2
+
+EAPI=8
+
+inherit cmake llvm.org
+
+DESCRIPTION="LLVM's Fortran frontend"
+HOMEPAGE="https://flang.llvm.org/"
+
+LICENSE="Apache-2.0-with-LLVM-exceptions"
+SLOT="${LLVM_MAJOR}/${LLVM_SOABI}"
+IUSE="+debug test"
+RESTRICT="!test? ( test )"
+
+DEPEND="
+	~llvm-core/clang-${PV}[debug=]
+	~llvm-core/llvm-${PV}[debug=]
+	~llvm-core/mlir-${PV}[debug=]
+"
+RDEPEND="
+	${DEPEND}
+"
+BDEPEND="
+	test? (
+		dev-python/lit
+	)
+"
+
+LLVM_COMPONENTS=( flang cmake )
+LLVM_TEST_COMPONENTS=( clang/test/Driver mlir/test/lib )
+llvm.org_set_globals
+
+src_configure() {
+	local mycmakeargs=(
+		-DCMAKE_INSTALL_PREFIX="${EPREFIX}/usr/lib/llvm/${LLVM_MAJOR}"
+
+		-DLLVM_ROOT="${ESYSROOT}/usr/lib/llvm/${LLVM_MAJOR}"
+		-DCLANG_RESOURCE_DIR="../../../clang/${LLVM_MAJOR}"
+
+		-DBUILD_SHARED_LIBS=OFF
+		-DMLIR_LINK_MLIR_DYLIB=ON
+		# flang does not feature a dylib, so do not install libraries
+		# or headers
+		-DLLVM_INSTALL_TOOLCHAIN_ONLY=ON
+
+		# TODO: always enable to obtain reproducible tools
+		-DFLANG_INCLUDE_TESTS=$(usex test)
+	)
+	use test && mycmakeargs+=(
+		-DLLVM_EXTERNAL_LIT="${EPREFIX}/usr/bin/lit"
+		-DLLVM_LIT_ARGS="$(get_lit_flags)"
+	)
+
+	# LLVM_ENABLE_ASSERTIONS=NO does not guarantee this for us, #614844
+	use debug || local -x CPPFLAGS="${CPPFLAGS} -DNDEBUG"
+	cmake_src_configure
+}
+
+src_test() {
+	# respect TMPDIR!
+	local -x LIT_PRESERVES_TMP=1
+	cmake_build check-flang
+}
+
+src_install() {
+	cmake_src_install
+
+	# move the runtime into 'lib' (sigh), until upstream resolves
+	# libdir support: https://github.com/llvm/llvm-project/issues/127538
+	mv "${ED}/usr/lib/llvm/${LLVM_MAJOR}"/{$(get_libdir),lib} || die
+}