--- clang-11.0.0.mainline.ebuild	2020-12-02 20:54:58.000000000 -0600
+++ clang-11.0.0.ebuild	2020-12-02 20:58:53.000000000 -0600
@@ -30,7 +30,7 @@
 
 LICENSE="Apache-2.0-with-LLVM-exceptions UoI-NCSA MIT"
 SLOT="$(ver_cut 1)"
-KEYWORDS="amd64 arm arm64 ppc64 x86 ~amd64-linux"
+KEYWORDS="amd64 arm arm64 ppc64 x86 ~amd64-linux ~x64-macos"
 IUSE="debug default-compiler-rt default-libcxx default-lld
 	doc +static-analyzer test xml kernel_FreeBSD ${ALL_LLVM_TARGETS[*]}"
 REQUIRED_USE="${PYTHON_REQUIRED_USE}
@@ -75,6 +75,10 @@
 # Therefore: use sys-devel/clang[${MULTILIB_USEDEP}] only if you need
 # multilib clang* libraries (not runtime, not wrappers).
 
+PATCHES=(
+	"${FILESDIR}"/11.0.0/prefix-dirs.patch
+)
+
 pkg_setup() {
 	LLVM_MAX_SLOT=${SLOT} llvm_pkg_setup
 	python-single-r1_pkg_setup
@@ -88,6 +92,11 @@
 	llvm.org_src_prepare
 
 	mv ../clang-tools-extra tools/extra || die
+
+	# add Gentoo Portage Prefix for Darwin (see prefix-dirs.patch)
+	sed -i -e "s|@GENTOO_PORTAGE_EPREFIX@|${EPREFIX}/|g" \
+		lib/Frontend/InitHeaderSearch.cpp \
+		lib/Driver/ToolChains/Darwin.cpp
 }
 
 check_distribution_components() {