slow "make clean"

[Ralf Hemmecke]

I've a project that must use subdir-objects, because of filename clashes 
in subdirectories (non-recursive build).

AM_INIT_AUTOMAKE([-Wall -Werror foreign subdir-objects])

I just have

lib_LTLIBRARIES = libfoo.la
check_PROGRAMS = ${TESTSUITE_TESTS} ${TESTSUITE_XFAIL_TESTS}

but quite a lot of files.

The generated Makefile contains a target "mostlyclean-compile" which has 
about 1500 lines that look like

  -rm -f src/foo/foo.$(OBJEXT)
  -rm -f src/foo/foo.lo
  ...

Of course it takes ages to say "make clean". About 10 sec.

Wouldn't it be faster if there were just one call to rm or at least 
block the number of arguments to rm so that the maximal argument lenght 
is not exceeded?

Any idea how I can speed that up?

Ralf