Remove BuildRoot definition

None of currently supported distributions need that.
It was needed last for EL5 which is EOL now

Signed-off-by: Igor Gnatenko <ignatenkobrain@fedoraproject.org>

linux-libertine-fonts.spec

@@ -26,7 +26,6 @@ Source2:        %{name}-biolinum-fontconfig.conf
 Source3:        %{name}-libertine-metrics-alias-fontconfig.conf
 Source4:        libertine.metainfo.xml
 Source5:        biolinum.metainfo.xml
-BuildRoot:      %(mktemp -ud %{_tmppath}/%{name}-%{version}-%{release}-XXXXXX)
 
 BuildArch:      noarch
 BuildRequires:  fontpackages-devel