go-native: don't use host /var/tmp for temp build artifacts

Similar to a recent change for go-cross we can potentially run in to a
build failure:

  go tool dist: mkdtemp(/var/tmp/go-cbuild-A0rrP5): No such file or directory

when the host doesn't have a /var/tmp or when the permissions don't
allow for the creation of the temporary directory. Instead of relying
on /var/tmp we create and use a temporary directory in the $WORKDIR to
work around this issue. This is passed to the build via the TMPDIR
environment variable.

Signed-off-by: Mark Asselstine <mark.asselstine@windriver.com>
Signed-off-by: Bruce Ashfield <bruce.ashfield@windriver.com>

recipes-devtools/go-cross/go-native.inc

@@ -11,6 +11,10 @@ do_compile() {
     export GOBIN="${B}/bin"
     rm -rf ${GOBIN}
     mkdir ${GOBIN}
+
+    export TMPDIR=${WORKDIR}/build-tmp
+    mkdir ${WORKDIR}/build-tmp
+
     cd src
     ./make.bash --host-only
 }