Make Fastpfor use libc++

fastpfor/Makefile

@@ -3,6 +3,7 @@ SHELL:=/bin/bash
 caf:
 	git clone https://github.com/lemire/FastPFor
 	pushd FastPFor && git checkout 8030e3808f857cc12d1d09e264f1ad2a05b1964a # master at the time of writing
+	patch FastPFor/CMakeLists.txt libcpp.patch
 	bash ../ubuntu1804.sh make impl
 	make package
 

fastpfor/libcpp.patch

@@ -0,0 +1,15 @@
+diff --git a/CMakeLists.txt b/CMakeLists.txt
+index d8cf6d2..519e260 100644
+--- a/CMakeLists.txt
++++ b/CMakeLists.txt
+@@ -83,8 +83,8 @@ elseif(${CMAKE_CXX_COMPILER_ID} STREQUAL "Clang" OR ${CMAKE_CXX_COMPILER_ID} STR
+     if (CXX_COMPILER_VERSION VERSION_LESS 4.2.1)
+         message(STATUS  "Clang version must be at least 4.2.1!" )
+     endif()
+-    set (CMAKE_CXX_FLAGS_RELEASE "-Wall -Wcast-align -O3 -DNDEBUG -std=c++11 -DHAVE_CXX0X -msse4.1 -march=native")
+-    set (CMAKE_CXX_FLAGS_DEBUG   "-Wall -Wcast-align -ggdb  -std=c++11 -DHAVE_CXX0X -msse4.1 -march=native")
++    set (CMAKE_CXX_FLAGS_RELEASE "-Wall -Wcast-align -O3 -DNDEBUG -std=c++11 -DHAVE_CXX0X -msse4.1 -march=native -stdlib=libc++")
++    set (CMAKE_CXX_FLAGS_DEBUG   "-Wall -Wcast-align -ggdb  -std=c++11 -DHAVE_CXX0X -msse4.1 -march=native -stdlib=libc++")
+     set (CMAKE_C_FLAGS_RELEASE "-Wall -Wcast-align -O3 -DNDEBUG -std=c99 -msse4.1 -march=native")
+     set (CMAKE_C_FLAGS_DEBUG   "-Wall -Wcast-align -ggdb  -std=c99 -msse4.1 -march=native")
+ elseif(WIN32)