llvm-runtimes/offload: 21.x now requires CXX=clang++ for deviceRTL

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

llvm-runtimes/offload/metadata.xml

@@ -5,6 +5,10 @@
 		<email>llvm@gentoo.org</email>
 	</maintainer>
 	<use>
+		<flag name="clang">
+			Force building using installed clang (rather than
+			the default CC/CXX).
+		</flag>
 		<flag name="ompt">Enable OpenMP Tools Interface support</flag>
 	</use>
 	<upstream>

llvm-runtimes/offload/offload-21.0.0.9999.ebuild

@@ -4,14 +4,19 @@
 EAPI=8
 
 PYTHON_COMPAT=( python3_{10..13} )
-inherit cmake llvm.org python-any-r1 toolchain-funcs
+inherit cmake crossdev flag-o-matic llvm.org python-any-r1
+inherit toolchain-funcs
 
 DESCRIPTION="OpenMP offloading support"
 HOMEPAGE="https://openmp.llvm.org"
 
 LICENSE="Apache-2.0-with-LLVM-exceptions || ( UoI-NCSA MIT )"
 SLOT="0/${LLVM_SOABI}"
-IUSE="+debug ompt test llvm_targets_AMDGPU llvm_targets_NVPTX"
+IUSE="+clang +debug ompt test llvm_targets_AMDGPU llvm_targets_NVPTX"
+REQUIRED_USE="
+	llvm_targets_AMDGPU? ( clang )
+	llvm_targets_NVPTX? ( clang )
+"
 RESTRICT="!test? ( test )"
 
 RDEPEND="
@@ -30,6 +35,7 @@ DEPEND="
 BDEPEND="
 	dev-lang/perl
 	virtual/pkgconfig
+	clang? ( llvm-core/clang )
 	llvm_targets_AMDGPU? ( llvm-core/clang[llvm_targets_AMDGPU] )
 	llvm_targets_NVPTX? ( llvm-core/clang[llvm_targets_NVPTX] )
 	test? (
@@ -63,6 +69,17 @@ pkg_setup() {
 }
 
 src_configure() {
+	if use clang && ! is_crosspkg; then
+		# Only do this conditionally to allow overriding with
+		# e.g. CC=clang-13 in case of breakage
+		if ! tc-is-clang ; then
+			local -x CC=${CHOST}-clang
+			local -x CXX=${CHOST}-clang++
+		fi
+
+		strip-unsupported-flags
+	fi
+
 	# LLVM_ENABLE_ASSERTIONS=NO does not guarantee this for us, #614844
 	use debug || local -x CPPFLAGS="${CPPFLAGS} -DNDEBUG"
 
@@ -115,11 +132,6 @@ src_configure() {
 	)
 
 	cmake_src_configure
-
-	if [[ ${build_devicertl} == FALSE ]]; then
-		# clang requires libomptarget.devicertl.a, but it can be empty
-		> "${BUILD_DIR}"/libomptarget.devicertl.a || die
-	fi
 }
 
 src_test() {
@@ -128,12 +140,3 @@ src_test() {
 
 	cmake_build check-offload
 }
-
-src_install() {
-	cmake_src_install
-
-	if [[ ! -f ${ED}/usr/$(get_libdir)/libomptarget.devicertl.a ]]
-	then
-		dolib.a "${BUILD_DIR}"/libomptarget.devicertl.a
-	fi
-}