libcxx: also build static versoin.

Fixes #4115.

srcpkgs/libcxx/template

@@ -1,7 +1,7 @@
 # Template file for 'libcxx'
 pkgname=libcxx
 version=3.8.0
-revision=3
+revision=4
 build_style=cmake
 hostmakedepends="cmake"
 case "$XBPS_TARGET_MACHINE" in
@@ -32,12 +32,31 @@ post_extract() {
 		sed -i 's/!defined(_GCC_MAX_ALIGN_T)/& \&\& !defined(__DEFINED_max_align_t)/' include/stddef.h
 	esac
 }
-
+post_configure() {
+	(
+	mkdir -p ${wrksrc}/build-static
+	cd ${wrksrc}/build-static
+	cmake ${configure_args} -DLIBCXX_ENABLE_SHARED=OFF ..
+	)
+}
+post_build() {
+	(
+	cd ${wrksrc}/build-static
+	${make_cmd} ${makejobs} ${make_build_args} ${make_build_target}
+	)
+}
+post_install() {
+	(
+	cd ${wrksrc}/build-static
+	${make_cmd} DESTDIR=${DESTDIR} ${make_install_args} ${make_install_target}
+	)
+}
 libcxx-devel_package() {
 	short_desc+=" - development files"
 	depends="${sourcepkg}>=${version}_${revision}"
 	pkg_install() {
 		vmove usr/include
 		vmove "usr/lib/*.so"
+		vmove "usr/lib/*.a"
 	}
 }