Fix libgit2 Mac build (again)

LIBSSH2_INCLUDE_DIR = /usr/local/include/

Author: Ben Chatelain

Diff for: script/update_libgit2

@@ -22,7 +22,11 @@ fi
 mkdir build
 cd build
 
-cmake -DBUILD_SHARED_LIBS:BOOL=OFF -DBUILD_CLAR:BOOL=OFF -DTHREADSAFE:BOOL=ON ..
+cmake -DBUILD_SHARED_LIBS:BOOL=OFF \
+	-DLIBSSH2_INCLUDE_DIR:PATH=/usr/local/include/ \
+	-DBUILD_CLAR:BOOL=OFF \
+	-DTHREADSAFE:BOOL=ON \
+	..
 cmake --build .
 
 product="libgit2.a"