rpmbuild: Change to $rootdir prior running the rpmbuild

This step was accidently removed by 47ee30d3e3.

Fixes issue #2332.

Signed-off-by: Michal Berger <michallinuxstuff@gmail.com>
Change-Id: I7ad9490715567b9a3a4c48ce67f3b038956654cd
Reviewed-on: https://review.spdk.io/gerrit/c/spdk/spdk/+/11174
Reviewed-by: Dong Yi <dongx.yi@intel.com>
Reviewed-by: Tomasz Zawadzki <tomasz.zawadzki@intel.com>
Reviewed-by: Jim Harris <james.r.harris@intel.com>
Community-CI: Broadcom CI <spdk-ci.pdl@broadcom.com>
Tested-by: SPDK CI Jenkins <sys_sgci@intel.com>

rpmbuild/rpm.sh

@@ -140,6 +140,8 @@ build_rpm() (
 	# the .spec.
 	: > "$_sourcedir/spdk-$version.tar.gz"
 
+	cd "$rootdir"
+
 	printf '* Starting rpmbuild...\n'
 	rpmbuild --clean --nodebuginfo "${macros[@]}" --build-in-place -ba "$spec"
 )