Fix rpmlint warnings

contrib/mercurial.spec:9: W: hardcoded-path-in-buildroot-tag /tmp/build.%{name}-%{version}-%{release}
A path is hardcoded in your Buildroot tag. It should be replaced by something
like %{_tmppath}/%name-root.

contrib/mercurial.spec:31: W: rpm-buildroot-usage %prep rm -rf $RPM_BUILD_ROOT
$RPM_BUILD_ROOT should not be touched during %build or %prep stage, as it will
break short circuiting.

contrib/mercurial.spec

@@ -1,78 +1,78 b''
 Summary: Mercurial -- a distributed SCM
 Name: mercurial
 Version: snapshot
 Release: 0
 License: GPL
 Group: Development/Tools
 Source: http://www.selenic.com/mercurial/release/%{name}-%{version}.tar.gz
 URL: http://www.selenic.com/mercurial
-BuildRoot: /tmp/build.%{name}-%{version}-%{release}
+BuildRoot: %{_tmppath}/%{name}-%{version}-%{release}-root
 
 # From the README:
 #
 #   Note: some distributions fails to include bits of distutils by
 #   default, you'll need python-dev to install. You'll also need a C
 #   compiler and a 3-way merge tool like merge, tkdiff, or kdiff3.
 #
 # python-devel provides an adequate python-dev.  The merge tool is a
 # run-time dependency.
 #
 BuildRequires: python >= 2.3, python-devel, make, gcc, asciidoc, xmlto
 
 %define pythonver %(python -c 'import sys;print ".".join(map(str, sys.version_info[:2]))')
 %define pythonlib %{_libdir}/python%{pythonver}/site-packages/%{name}
 %define hgext %{_libdir}/python%{pythonver}/site-packages/hgext
 
 %description
 Mercurial is a fast, lightweight source control management system designed
 for efficient handling of very large distributed projects.
 
 %prep
-rm -rf $RPM_BUILD_ROOT
 %setup -q
 
 %build
 make all
 
 %install
+rm -rf $RPM_BUILD_ROOT
 python setup.py install --root $RPM_BUILD_ROOT --prefix %{_prefix}
 make install-doc DESTDIR=$RPM_BUILD_ROOT MANDIR=%{_mandir}
 
 install contrib/hgk          $RPM_BUILD_ROOT%{_bindir}
 install contrib/convert-repo $RPM_BUILD_ROOT%{_bindir}/mercurial-convert-repo
 install contrib/hg-ssh       $RPM_BUILD_ROOT%{_bindir}
 install contrib/git-viz/{hg-viz,git-rev-tree} $RPM_BUILD_ROOT%{_bindir}
 
 bash_completion_dir=$RPM_BUILD_ROOT%{_sysconfdir}/bash_completion.d
 mkdir -p $bash_completion_dir
 install contrib/bash_completion $bash_completion_dir/mercurial.sh
 
 zsh_completion_dir=$RPM_BUILD_ROOT%{_datadir}/zsh/site-functions
 mkdir -p $zsh_completion_dir
 install contrib/zsh_completion $zsh_completion_dir/_mercurial
 
 lisp_dir=$RPM_BUILD_ROOT%{_datadir}/emacs/site-lisp
 mkdir -p $lisp_dir
 install contrib/mercurial.el $lisp_dir
 
 # We don't want this, do we?
 rm -f $RPM_BUILD_ROOT%{pythonlib}/../mercurial-*-py2.5.egg-info
 
 %clean
 rm -rf $RPM_BUILD_ROOT
 
 %files
 %defattr(-,root,root,-)
 %doc CONTRIBUTORS COPYING doc/README doc/hg*.txt doc/hg*.html doc/ja *.cgi
 %{_mandir}/man?/hg*.gz
 %{_sysconfdir}/bash_completion.d/mercurial.sh
 %{_datadir}/zsh/site-functions/_mercurial
 %{_datadir}/emacs/site-lisp/mercurial.el
 %{_bindir}/hg
 %{_bindir}/hgk
 %{_bindir}/hg-ssh
 %{_bindir}/hg-viz
 %{_bindir}/git-rev-tree
 %{_bindir}/mercurial-convert-repo
 %{pythonlib}
 %{hgext}