build-unit-test-docker: Fix permissions

Using --create-dirs on curl makes directories with 0750 permissions.
This prevents our builder from reading the file inside the directory.
Create it with `mkdir` instead so that we end up with the correct
permissions.

Change-Id: If871d614a05fff6d1198c6e0de3ba76b48a02da0
Signed-off-by: William A. Kennington III <wak@google.com>
diff --git a/build-unit-test-docker.sh b/build-unit-test-docker.sh
index 7c18dff..27729f8 100755
--- a/build-unit-test-docker.sh
+++ b/build-unit-test-docker.sh
@@ -228,7 +228,8 @@
 make install
 
 FROM openbmc-base as openbmc-function2
-RUN curl --create-dirs -L -o ${PREFIX}/include/function2/function.hpp https://raw.githubusercontent.com/Naios/function2/${PKG_REV['function2']}/include/function2/function2.hpp
+RUN mkdir ${PREFIX}/include/function2 && \
+curl -L -o ${PREFIX}/include/function2/function2.hpp https://raw.githubusercontent.com/Naios/function2/${PKG_REV['function2']}/include/function2/function2.hpp
 
 FROM openbmc-base as openbmc-googletest
 RUN curl -L https://github.com/google/googletest/archive/${PKG_REV['googletest']}.tar.gz | tar -xz && \