rpm: remove tmp folder created during install

nativesdk-rpm build is also affected by the stray /var/tmp
created during the rpm install. Remove it to fix QA Issue:
nativesdk-rpm installs files in /usr/local/oe-sdk-hardcoded-buildpath/sysroots/x86_64-pokysdk-linux/var/volatile, but it is expected to be empty [empty-dirs]

(From OE-Core rev: 28dd1e1a0965646c5736e3de91aad830311a797b)

Signed-off-by: Samuli Piippo <samuli.piippo@qt.io>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/recipes-devtools/rpm/rpm_4.17.0.bb

@@ -137,6 +137,9 @@ do_install:append:class-nativesdk() {
 do_install:append:class-target() {
     rm -rf ${D}/var
 }
+do_install:append:class-nativesdk() {
+    rm -rf ${D}${SDKPATHNATIVE}/var
+}
 
 do_install:append () {
 	sed -i -e 's:${HOSTTOOLS_DIR}/::g' \