dev-libs/libclc: Fix possible llvm/clang slot mismatch, #615754

Ensure that the LLVM slot with matching clang version is always used.
Otherwise, if you have a newer LLVM slot without clang, and an older
slot with clang, libclc got paths from the newer llvm-config and was
unable to find clang. Now the ebuild finds clang first, and uses
the llvm-config installed alongside it.

dev-libs/libclc/libclc-0.2.0_pre20170118.ebuild

@@ -39,9 +39,13 @@ DEPEND="${RDEPEND}
 	${PYTHON_DEPS}"
 
 src_configure() {
+	# we need to find llvm with matching clang version, so look for
+	# clang first, and then use llvm-config from the same location
+	local clang_path=$(type -P clang) || die
+
 	./configure.py \
 		--with-cxx-compiler="$(tc-getCXX)" \
-		--with-llvm-config="$(type -P llvm-config)" \
+		--with-llvm-config="${clang_path%/*}/llvm-config" \
 		--prefix="${EPREFIX}/usr" || die
 }