kbuild: srcrpm-pkg: create source package without cleaning

If you run 'make (src)rpm-pkg', all objects are lost due to 'make clean',
which makes the incremental builds impossible.

Instead of cleaning, pass the exclude list to tar's --exclude-from
option.

Previously, the .config was contained in the source tarball.

With this commit, the source rpm consists of separate linux.tar.gz
and .config.

Remove stale comments. Now, 'make (src)rpm-pkg' works with O= option.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

scripts/package/mkspec

@@ -47,7 +47,8 @@ sed -e '/^DEL/d' -e 's/^\t*//' <<EOF
 	Group: System Environment/Kernel
 	Vendor: The Linux Community
 	URL: https://www.kernel.org
-$S	Source: kernel-$__KERNELRELEASE.tar.gz
+$S	Source0: linux.tar.gz
+$S	Source1: .config
 	Provides: $PROVIDES
 $S	BuildRequires: bc binutils bison dwarves
 $S	BuildRequires: (elfutils-libelf-devel or libelf-devel) flex
@@ -83,9 +84,8 @@ $S$M	This package provides kernel headers and makefiles sufficient to build modu
 $S$M	against the $__KERNELRELEASE kernel package.
 $S$M
 $S	%prep
-$S	%setup -q
-$S	rm -f scripts/basic/fixdep scripts/kconfig/conf
-$S	rm -f tools/objtool/{fixdep,objtool}
+$S	%setup -q -n linux
+$S	cp %{SOURCE1} .
 $S
 $S	%build
 $S	$MAKE %{?_smp_mflags} KERNELRELEASE=$KERNELRELEASE KBUILD_BUILD_VERSION=%{release}