external_deps: ensure existence of cmake dir

Don't fail in install target if there's no lib/cmake

Author: slipher

external_deps/build.sh

@@ -977,6 +977,7 @@ build_install() {
 	mkdir -p "${PKG_PREFIX}/bin"
 	mkdir -p "${PKG_PREFIX}/include"
 	mkdir -p "${PKG_PREFIX}/lib"
+	mkdir -p "${PKG_PREFIX}/lib/cmake"
 
 	# Remove all unneeded files
 	rm -rf "${PKG_PREFIX}/man"