don't prune kernel-devel in the %with_headers install section

commit c1bdfc8b broke the build on s390 since it is headers only,
and had nothing installed in /usr/src/kernels... since kernel-devel
is only produced when there's a BuildKernel, just prune '*.cmd'
when doing BuildKernel for the same net result.

kernel.spec

@@ -1572,9 +1572,12 @@ BuildKernel() {
     done
 
     # Move the devel headers out of the root file system
-    mkdir -p $RPM_BUILD_ROOT/usr/src/kernels
+    mkdir -p $RPM_BUILD_ROOT/$DevelDir
     mv $RPM_BUILD_ROOT/lib/modules/$KernelVer/build $RPM_BUILD_ROOT/$DevelDir
     ln -sf ../../..$DevelDir $RPM_BUILD_ROOT/lib/modules/$KernelVer/build
+
+    # prune junk from kernel-devel
+    find $RPM_BUILD_ROOT/usr/src/kernels -name ".*.cmd" -exec rm -f {} \;
 }
 
 ###
@@ -1693,8 +1696,6 @@ find $RPM_BUILD_ROOT/usr/include \
      \( -name .install -o -name .check -o \
      	-name ..install.cmd -o -name ..check.cmd \) | xargs rm -f
 
-find $RPM_BUILD_ROOT/usr/src/kernels -name ".*.cmd" -exec rm -f {} \;
-
 # glibc provides scsi headers for itself, for now
 rm -rf $RPM_BUILD_ROOT/usr/include/scsi
 rm -f $RPM_BUILD_ROOT/usr/include/asm*/atomic.h