ipmitool: Allow devtool modify

The folder doesn't exist during the devtool build so
build fails. Make the folder so build can pass.

Tested: devtool build passes

Change-Id: I821de34542a12b17399c05ac8fb4b83237cb8412
Signed-off-by: James Feist <james.feist@linux.intel.com>
diff --git a/recipes-phosphor/ipmi/ipmitool_%.bbappend b/recipes-phosphor/ipmi/ipmitool_%.bbappend
index 8f390f5..a6a8198 100644
--- a/recipes-phosphor/ipmi/ipmitool_%.bbappend
+++ b/recipes-phosphor/ipmi/ipmitool_%.bbappend
@@ -23,6 +23,7 @@
 do_compile_prepend() {
     # copy the SRC_URI version of enterprise-numbers
     # to the build dir to prevent a fetch
+    mkdir -p "${WORKDIR}/build"
     cp "${WORKDIR}/enterprise-numbers" "${WORKDIR}/build/enterprise-numbers"
 }