Build libcxx and libcxxabi statically for armv7 and test building a C++ hello world

patches/mingw-0002.patch

@@ -0,0 +1,27 @@
+From ac615730861d430aa38435ecb55031316062d6f6 Mon Sep 17 00:00:00 2001
+From: =?UTF-8?q?Martin=20Storsj=C3=B6?= <martin@martin.st>
+Date: Fri, 25 Aug 2017 12:02:02 +0300
+Subject: [PATCH 2/2] crt: Include _strftime_l in msvcrt.def.in
+
+This fixes linking of libc++, which uses this function. libc++
+needs a msvcrt new enough to provide this function (present
+since msvcr90 in the numbered msvcrt DLLs).
+---
+ mingw-w64-crt/lib-common/msvcrt.def.in | 1 +
+ 1 file changed, 1 insertion(+)
+
+diff --git a/mingw-w64-crt/lib-common/msvcrt.def.in b/mingw-w64-crt/lib-common/msvcrt.def.in
+index c63edd2..35c685d 100644
+--- a/mingw-w64-crt/lib-common/msvcrt.def.in
++++ b/mingw-w64-crt/lib-common/msvcrt.def.in
+@@ -1481,6 +1481,7 @@ strcspn
+ strerror
+ ; strerror_s replaced by emu
+ strftime
++_strftime_l
+ strlen
+ strncat
+ strncat_s
+-- 
+2.7.4
+