jsoncpp 1.7.2 use mkdir -p instead of mkdir

Use mkdir -p instead of mkdir so that the package does not fail if the
dir exists.

jsoncpp/PKGBUILD

@@ -2,7 +2,7 @@
 
 pkgname="jsoncpp"
 pkgver=1.7.2
-pkgrel=2
+pkgrel=3
 pkgdesc="A C++ library for interacting with JSON"
 arch=('any')
 url="https://github.com/open-source-parsers/jsoncpp"
@@ -20,7 +20,7 @@ prepare() {
 }
 
 build() {
-  mkdir "${srcdir}/build-${CARCH}"
+  mkdir -p "${srcdir}/build-${CARCH}"
   cd "${srcdir}/build-${CARCH}"
 
   cmake \