do not try to crate build directory if already exists

From: Gergely Imreh <imrehg@gmail.com>

Signed-off-by: Gergely Imreh <imrehg@gmail.com>
---
 hugin/PKGBUILD |    4 +++-
 1 files changed, 3 insertions(+), 1 deletions(-)

diff --git a/hugin/PKGBUILD b/hugin/PKGBUILD
index aaeab4e..db7b164 100644
--- a/hugin/PKGBUILD
+++ b/hugin/PKGBUILD
@@ -19,7 +19,9 @@ md5sums=('0c88afbd7f8159aac29404ff40370400')
 
 build() {
   cd ${srcdir}/${pkgname}-${pkgver}
-  mkdir mybuild
+  if [ ! -d 'mybuild' ]; then
+    mkdir mybuild
+  fi
   cd mybuild
   cmake \
     -DCMAKE_INSTALL_PREFIX=/usr \